I wish the monuments were a little more consistent with regards to how hard it is to meet the conditions for an offering. While their upgraded reinforce actions range from meh to great, blocking the wastelands from showing up is always a good thing. Some offerings are largely down to luck or extremely convoluted play. Below are my thoughts on the offering and reinforce actions of the monuments. I don't have an easy reference for all the events, so I can't list them. I do kind of wish you could pick which monuments you play with.
Arch of the Golden Sun
Offering - End your turn with 2+ foes on or adjacent to your space.
Difficulty 3/5 - If you get lucky, two foes will just happen to end up next to each other. There are ways to move foes, like the potion, but that's not always an option. Once the foes are in place, multiple people can tag team the location to finish this off fairly quickly. This does typically mean you are letting foes live instead of just taking them out. That might be okay if you have other heroic actions to do, but less great if battling would have been your choice otherwise.
Reinforce - Spend 5 spirit to unlock a virtue and get two random treasures.
Rating 5/5 - Just flat out better than the Citadel virtue unlock. Very simple.
Argent Oak
Offering - Gain a corruption.
Difficulty 1/5 - Although we have been trained to generally avoid corruptions, they aren't hard to get if you go looking for them. Obviously, the risk of losing the entire game is a factor here, but that doesn't stop the offering from being easy to accomplish.
Reinforce - Spend any number of items to remove an equal number of corruptions.
Rating 4/5 - I rate this one highly because it replaces the existing Sanctuary corruption removal with a different version and this one lets you keep your precious spirit for more virtues, etc. Being that this is broadly any item, you can toss a few potions or maybe gear to clear you right up. You also don't have to worry about getting "better value" by clearing two corruptions for 5 spirit instead of one.
Cenotaph of the First Prophet
Offering - Defeat a foe in a wasteland
Difficulty 2/5 - After having wastelands spewed across the board, this goal becomes pretty easy. It becomes more likely as the game goes on. You'll definitely have more spaces that qualify than for the Tower Shard offering.
Reinforce - Spend 4 spirit to gain an active virtue tile from outside of the game.
Rating 5/5* - This is probably the craziest monument power. It opens up a world of possibilities combining virtues in new ways. BUT it's really annoying logistically (hence the asterisk). Having to have the 3x unused heroes virtues to hand to choose from is a bit tedious. Even playing at four players, that would still be 18 virtue tiles for me. Then players have to look through all the options to decide which one they want (hopefully while it's not their turn). To be fair though, a lot of the virtues aren't useful to heroes other than the original. It's a double edged sword of being simultaneously amazing but at the cost of really gunking up the flow of the game.
Colossus of Bjorn
Offering - Lose 8+ warriors from a battle card.
Difficulty 4/5 - On the face of it, this one should be pretty easy assuming you amass a lot of warriors (which some characters are very good at). However, in my experience, a lot of the early fights you have against 3 pip level 2 and 3 monsters don't inflict this amount of damage. I also recall battle cards that make you lose 7 warriors, which is extra cheeky. I haven't memorized every battle card, so maybe there are specific foes that make this incredibly easy, but we found that it didn't make progress until month 4 or 5. That a lot of time getting wastelands.
Reinforce - Place yourself and this building in a space without a building.
Rating 3/5 - It's a pretty unique power for a reinforce action, but still somewhat situational. It's definitely a welcome way to deal with a board plagued with wasteland spaces. It does require that the monument itself be in a useful place. If your hero is in the East and wants to be in the West, it doesn't help a lot if the Colossus is in the South, for example. You also lose the option of getting 12 warriors for 1 spirit from a regular Village, which is a very popular reinforce action in my games.
Endless Necropolis
Offering - Spend or lose a treasure.
Difficulty 3/5 - This has to happen organically, you cannot "just spend a treasure" to qualify. Only some treasures have spend options on them and then there is usually a condition for use. Some market manipulation might be in order for this to get done in a timely manner. You could lose a treasure any time you have to lose an item, which feels pretty bad, but could be a shortcut with the right foes. This one isn't extremely hard, but definitely could be tricky with bad luck.
Reinforce - Spend 1 spirit to remove any number of skulls from this building and return them to the supply. [It can hold any number of skulls]
Rating 1/5 - Meh. Obviously, the real power is the infinite skull capacity of the building. The action itself is more of a flush the toilet maintenance thing. It's a great place for Doom Skulls to go, but by the time you get it built, you may have already had to place a few anyway. I guess it could make a Haunted Recluse with Soulreaper nearly invincible, which is fun. Once again, you lose the enhanced village reinforce, which is a bummer.
Moonstone Temple
Offering - Complete a battle without using any advantages.
Difficulty: 1/5 - Pretty easy to trigger, but it does mean you need to be prepared for the losses or prepared for gaining a curse or two.
Reinforce - Spend 10 spirit to Battle and Cleanse any number of times this turn.
Rating 3/5 - Kind of wild if you can make good use of it. One assumes you get 2 spirit back for each battle or cleanse you do. If you managed to line up 5 of them, it pays for itself. The limitation is that these opportunities need to be near-ish to the monument, so having tons of movement would be key, which might involve spending 1 more spirit for double movement. Could lead to a very long turn if you have a bunch of battles.
Nightmare Cage
Offering - End your turn with 4+ skulls on or adjacent to your space.
Difficulty 2/5 - It's pretty easy to stand between two building at various places around the board. Normally, every region would start with four skulls on two buildings, possibly where you could stand between them even. However, the monuments may replace the buildings that should have started with skulls on them. It's also possible the starting skulls are not on building near each other. It's easy enough to arrange any falling skulls to meet this criteria if needed. The only downside is that clearing skulls is a go-to heroic action, especially turn one, so you might deny yourself that easy head start to the game. If you have any events that will be adding skulls, things could get pretty spicy. If you have a completed Necropolis, this becomes fairly trivial.
Reinforce - Spend 20 warriors to remove a foe.
Rating 2/5 - I think my main reason for not rating this higher is the cost. Sure, for a 5 pip level 4 foe, this might be a bargain, but those are few and far between. For other foes, a lot of players can get through a battle with less than 20 warriors lost. It does let you remove a foe outside of a Heroic action, but so do some other virtues and treasures. I'm sure they arrived at the cost after testing, but I don't think I will use it often personally. I might have liked an incremental cost, say 5 warriors per level of the foe (10/15/20) but maybe that's overly complicated?
Tower Shard
Offering - Defeat a foe in a space adjacent to the Tower.
Difficulty 5/5 - In my game with this monument, only one foe spawned naturally next to the tower. You would think maybe the app would help you out, knowing this monument is in play, but alas. I have no idea what the algorithm behind foe placement is like, but only 10% (6/60) of the spaces are tower adjacent. Again, being able to move foes around is not a guarantee. Also, it specifies that it must be a Battle action.
Reinforce - Spend 1 spirit for 2 potions.
Rating 1/5 - All I can say is whoopdy doo. Sure, potions are nice and more is better. This monument is a real pain to get built for such a ho hum power. I guess the Relic Hunter could make good use of it.
Arch of the Golden Sun
Offering - End your turn with 2+ foes on or adjacent to your space.
Difficulty 3/5 - If you get lucky, two foes will just happen to end up next to each other. There are ways to move foes, like the potion, but that's not always an option. Once the foes are in place, multiple people can tag team the location to finish this off fairly quickly. This does typically mean you are letting foes live instead of just taking them out. That might be okay if you have other heroic actions to do, but less great if battling would have been your choice otherwise.
Reinforce - Spend 5 spirit to unlock a virtue and get two random treasures.
Rating 5/5 - Just flat out better than the Citadel virtue unlock. Very simple.
Argent Oak
Offering - Gain a corruption.
Difficulty 1/5 - Although we have been trained to generally avoid corruptions, they aren't hard to get if you go looking for them. Obviously, the risk of losing the entire game is a factor here, but that doesn't stop the offering from being easy to accomplish.
Reinforce - Spend any number of items to remove an equal number of corruptions.
Rating 4/5 - I rate this one highly because it replaces the existing Sanctuary corruption removal with a different version and this one lets you keep your precious spirit for more virtues, etc. Being that this is broadly any item, you can toss a few potions or maybe gear to clear you right up. You also don't have to worry about getting "better value" by clearing two corruptions for 5 spirit instead of one.
Cenotaph of the First Prophet
Offering - Defeat a foe in a wasteland
Difficulty 2/5 - After having wastelands spewed across the board, this goal becomes pretty easy. It becomes more likely as the game goes on. You'll definitely have more spaces that qualify than for the Tower Shard offering.
Reinforce - Spend 4 spirit to gain an active virtue tile from outside of the game.
Rating 5/5* - This is probably the craziest monument power. It opens up a world of possibilities combining virtues in new ways. BUT it's really annoying logistically (hence the asterisk). Having to have the 3x unused heroes virtues to hand to choose from is a bit tedious. Even playing at four players, that would still be 18 virtue tiles for me. Then players have to look through all the options to decide which one they want (hopefully while it's not their turn). To be fair though, a lot of the virtues aren't useful to heroes other than the original. It's a double edged sword of being simultaneously amazing but at the cost of really gunking up the flow of the game.
Colossus of Bjorn
Offering - Lose 8+ warriors from a battle card.
Difficulty 4/5 - On the face of it, this one should be pretty easy assuming you amass a lot of warriors (which some characters are very good at). However, in my experience, a lot of the early fights you have against 3 pip level 2 and 3 monsters don't inflict this amount of damage. I also recall battle cards that make you lose 7 warriors, which is extra cheeky. I haven't memorized every battle card, so maybe there are specific foes that make this incredibly easy, but we found that it didn't make progress until month 4 or 5. That a lot of time getting wastelands.
Reinforce - Place yourself and this building in a space without a building.
Rating 3/5 - It's a pretty unique power for a reinforce action, but still somewhat situational. It's definitely a welcome way to deal with a board plagued with wasteland spaces. It does require that the monument itself be in a useful place. If your hero is in the East and wants to be in the West, it doesn't help a lot if the Colossus is in the South, for example. You also lose the option of getting 12 warriors for 1 spirit from a regular Village, which is a very popular reinforce action in my games.
Endless Necropolis
Offering - Spend or lose a treasure.
Difficulty 3/5 - This has to happen organically, you cannot "just spend a treasure" to qualify. Only some treasures have spend options on them and then there is usually a condition for use. Some market manipulation might be in order for this to get done in a timely manner. You could lose a treasure any time you have to lose an item, which feels pretty bad, but could be a shortcut with the right foes. This one isn't extremely hard, but definitely could be tricky with bad luck.
Reinforce - Spend 1 spirit to remove any number of skulls from this building and return them to the supply. [It can hold any number of skulls]
Rating 1/5 - Meh. Obviously, the real power is the infinite skull capacity of the building. The action itself is more of a flush the toilet maintenance thing. It's a great place for Doom Skulls to go, but by the time you get it built, you may have already had to place a few anyway. I guess it could make a Haunted Recluse with Soulreaper nearly invincible, which is fun. Once again, you lose the enhanced village reinforce, which is a bummer.
Moonstone Temple
Offering - Complete a battle without using any advantages.
Difficulty: 1/5 - Pretty easy to trigger, but it does mean you need to be prepared for the losses or prepared for gaining a curse or two.
Reinforce - Spend 10 spirit to Battle and Cleanse any number of times this turn.
Rating 3/5 - Kind of wild if you can make good use of it. One assumes you get 2 spirit back for each battle or cleanse you do. If you managed to line up 5 of them, it pays for itself. The limitation is that these opportunities need to be near-ish to the monument, so having tons of movement would be key, which might involve spending 1 more spirit for double movement. Could lead to a very long turn if you have a bunch of battles.
Nightmare Cage
Offering - End your turn with 4+ skulls on or adjacent to your space.
Difficulty 2/5 - It's pretty easy to stand between two building at various places around the board. Normally, every region would start with four skulls on two buildings, possibly where you could stand between them even. However, the monuments may replace the buildings that should have started with skulls on them. It's also possible the starting skulls are not on building near each other. It's easy enough to arrange any falling skulls to meet this criteria if needed. The only downside is that clearing skulls is a go-to heroic action, especially turn one, so you might deny yourself that easy head start to the game. If you have any events that will be adding skulls, things could get pretty spicy. If you have a completed Necropolis, this becomes fairly trivial.
Reinforce - Spend 20 warriors to remove a foe.
Rating 2/5 - I think my main reason for not rating this higher is the cost. Sure, for a 5 pip level 4 foe, this might be a bargain, but those are few and far between. For other foes, a lot of players can get through a battle with less than 20 warriors lost. It does let you remove a foe outside of a Heroic action, but so do some other virtues and treasures. I'm sure they arrived at the cost after testing, but I don't think I will use it often personally. I might have liked an incremental cost, say 5 warriors per level of the foe (10/15/20) but maybe that's overly complicated?
Tower Shard
Offering - Defeat a foe in a space adjacent to the Tower.
Difficulty 5/5 - In my game with this monument, only one foe spawned naturally next to the tower. You would think maybe the app would help you out, knowing this monument is in play, but alas. I have no idea what the algorithm behind foe placement is like, but only 10% (6/60) of the spaces are tower adjacent. Again, being able to move foes around is not a guarantee. Also, it specifies that it must be a Battle action.
Reinforce - Spend 1 spirit for 2 potions.
Rating 1/5 - All I can say is whoopdy doo. Sure, potions are nice and more is better. This monument is a real pain to get built for such a ho hum power. I guess the Relic Hunter could make good use of it.