An Eternal Witness or Karmic Guide or Primeval Titan in those formats where its legal
If an opponent tries to destroy a creature with all of your Auras and Equipment attached to it, for two mana you can move all of them to another creature, or spread them between several creatures
However, since the printing of Prismatic Ending, Jeskai has come back and established itself as the more popular control variant, as the deck now has access to the two best removal spells in the format, Swords to Plowshares and Prismatic Ending, which means you have enough removal for creature decks and reliable ways to deal with problematic cards like Chalice of the Void and Aether Vial
Later, WotC changed this to a keyword ability called defender, and suddenly a whole world of creatures that werent Walls could not attack
The fact that Rooms don't appear at common rarity (according to MaRo) is raising further doubts about the strategy's consistency in draft