Minecraft Dungeons:Rune room

Rune rooms are hidden rooms that can grant access to runes that the player can collect, they will mostly consist of a narrow rampart over a purple void that will lead to a tower with a rune symbol. There is a button nearby, if a player presses this button, it will greet him/her with the respective rune. The exception to this is Obsidian Pinnacle, which features the rune in a regular room instead.

Mobs
No mobs of any kind ever spawn in these rooms.

ja:MCD:Rune room