Mutavault

Type: Land
Set: Champs and States #12 (rare)

{T}: Add {C}.
{1}: This land becomes a 2/2 creature with all creature types until end of turn. It's still a land.

Mutavault has 15 printings, first in Morningtide (2008). EDHREC ranks it #1,911 among Commander cards. It appears most in Magda, Brazen Outlaw decks (8,007 on EDHREC). 3 public decks on TCG run it. It has 2 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: legal
pioneer: legal
standard: not legal
brawl: legal

Public decks that run Mutavault

Everyone's Invited - Secret Lair Drop - WUBRG EDH Precon Decklist, led by Morophon, the Boundless
Landing Party - Star Trek Commander, led by Commander Spock
Party Time - Commander Legends: Battle for Baldur's Gate, led by Nalia de'Arnise

Commanders that run Mutavault most

Deck counts from EDHREC.

Magda, Brazen Outlaw: 8,007 decks
Voja, Jaws of the Conclave: 3,100 decks
Giada, Font of Hope: 2,438 decks
The Destined Warrior: 2,252 decks
Nalia de'Arnise: 1,904 decks
Morophon, the Boundless: 1,698 decks
Yuriko, the Tiger's Shadow: 1,654 decks
Black Panther, Wakandan King: 1,228 decks

Often played with Mutavault

Cards that show up in the same decks on EDHREC.

Rulings

2008-04-01: Although Mutavault has all creature types while it's animated, it does not have the changeling keyword ability.
2008-08-01: A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn't matter how long the permanent has been a creature.