Giving your creature indestructible can be a lifesaver if you need other stax pieces (I am assuming if you play Boromir, Warden of the Tower , you are playing a stax deck) to stay alive, or if you just want to beat down someone and survive a board wipe
At the most basic level, it can be a pseudo-protection spell by switching auras and equipment away from a creature thats about to die and suiting up something else
these events qualify players for Arena Championship 10
You hear someone ask Are you wearing jeans? to make sure Hurloon Wranglers denimwalk applies
Most of the time its used versus decks with x/1 creatures: Ragavan, Nimble Pilferer, Dragons Rage Channeler, Esper Sentinel, mana dorks, a Dwarf token, Inkmoth Nexus, etc
(More on Vaults below.) Every time you complete a Vault, you will receive three Wildcards (one rare and two uncommons) in addition to the individual cards noted above