Warforged

Colorshift
Other commander permanents you control have, "Whenever you Venture Into The Dungeon, you
may change the room text to, 'Create a 1/1
Colorless Warforged artifact creature token'."
At the beginning of your end step if you control
four or more colorless creatures, Venture Into
The Dungeon.
This spell costs {1} less to cast for each differently
named dungeon you've completed.