Reminds me of a game in which everyone is a pirate captain/admiral. Guilds have their own HQ. It can be attacked and raided by other guilds. An HQ gets successfully raided when the final defences have fallen. To do so, there's a timer running down from 5 minutes to 0. If 1 defence falls, the timer resets back to 5 minutes. Until the final line of defence has been reached. Then the final timer starts at 10 minutes. If the besieging guild is successful to breach the final line of defence, they've successfully raided. If the timer at any time hits 0, the attack is successfully repelled.
In that game there were also special event npc guilds. Ranging in difficulty: easy, medium, hard. Mostly aimed for: small, medium, large guilds. Irony is that buffed players could defeat alone easy and even medium event HQ's. Although the letter was tricky. Kinda reminds me of that. With the HQ kind of city and the naming. Might be wrong though. Could be just a guild HQ offering perks through buildings. Constructed with resources from raids. Might be the revisions "guild perks" thing.
In that game there were also special event npc guilds. Ranging in difficulty: easy, medium, hard. Mostly aimed for: small, medium, large guilds. Irony is that buffed players could defeat alone easy and even medium event HQ's. Although the letter was tricky. Kinda reminds me of that. With the HQ kind of city and the naming. Might be wrong though. Could be just a guild HQ offering perks through buildings. Constructed with resources from raids. Might be the revisions "guild perks" thing.