It is based on how many strongholds you have now, and how many rooms are unlocked. I believe (can't recall exactly since I have all the strongholds and all rooms are unlocked) you need to have 5 strongholds completely unlocked. Doesn't have to be decorated.

Six, not five, but you're right, the decoration percentage no longer matters for the conquest bonus. (It's +25 % per stronghold completely unlocked.)

That’s kinda lame, but super convenient. Is there a bonus for how many strongholds a guilds owns and unlocks?

Given the number of strongholds that were decorated to 100% with a mix of basic metal chairs, trophies and meat trees, it's actually a pretty good solution. People who care about the aesthetics of decorating can do so without feeling like they need to cram in a room full of junk just to finish off their conquest bonus, and people who only care about conquest can get their bonus without having to fark around placing hundreds of meat trees.

As for guilds, well, I believe that a guild is limited to one stronghold anyway, and it doesn't give any bonuses. Someone who knows better is welcome to correct that.

Given the number of strongholds that were decorated to 100% with a mix of basic metal chairs, trophies and meat trees, it's actually a pretty good solution. People who care about the aesthetics of decorating can do so without feeling like they need to cram in a room full of junk just to finish off their conquest bonus, and people who only care about conquest can get their bonus without having to fark around placing hundreds of meat trees.

 

As for guilds, well, I believe that a guild is limited to one stronghold anyway, and it doesn't give any bonuses. Someone who knows better is welcome to correct that.

You are correct. 1 stronghold for a guild --no bonus.