In multiplayer, a Caged Invader (and as such the associated invader dungeon) is more of a one-time thing. Since most modpacks are shipping with Lootr, this means that the dungeon is really only a problem for the first poor soul who encounters it and then free loot for anyone else who happens upon it.

A potential solution to that is to make the Caged Invader (the spawner) block persist, and spawn one per player, probably with some kind of cooldown so it doesn't spawn a horde if a group of people wander upon it.

Though that would also mean the block has to be unbreakable, so idk. Maybe not terribly useful?

Though that would also mean the block has to be unbreakable, so idk. Maybe not terribly useful?

Lootr mitigates this by making its chests (which replace vanilla loot chests) unbreakable unless they are being mined by a player who is sneaking.

A similar thing could be implemented for the Caged Invader block, possibly with the additional requirement of all players within its range having activated the spawner and/or killed its invader.