mtg epic cards Downfall | Throne of Eldraine epic mtg cards Rules Text:

In a multiplayer game, if Chains of Custody's owner leaves the game, the exiled card will return to the battlefield

Ardenn, Intrepid Archaeologist is no exception in that regard and has a standout keyword that may well increase its attractiveness massively to players who can make good use of it

Squirrel Mob in particular has some great flavor text, so I highlight it here

If the creature is already monstrous when the monstrosity ability resolves, nothing happens

So, you don't lose it if you go down permanents and drop below the requisite

the Doctor would offer the shelter and benefits of the TARDIS to anybody, but the card also opens the door to interesting political plays