Aside from the flattering reward of having Yroa in unadulterated maid outfit, Golmaris also voiced a message about state and consequence if this dungeon were to happen to be closed and destroyed.
It was relayed to them that the entirety of this dungeon was linked to Yroa as an existence, and as the result, both of them would be doomed to perish if one of the two were expurgated.
Obviously, that was an utter lie—one of the very first critical lie that Yroa exhaled from his throat, in fact, since Yroa could just leave the development of this dungeon into a withering halt where everything staled just for it to reach entropy—and make a new dungeon somewhere else.
As a Living Dungeon Core, the dungeon might be obligated to have Yroa to exist, but Yroa didn't need the dungeon to stand for him to exist.