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
A triggered ability is an ability that starts with the words when, whenever, or at. These go on the stack automatically when their condition is met
So, you don't lose it if you go down permanents and drop below the requisite
In a multiplayer game, if Chains of Custody's owner leaves the game, the exiled card will return to the battlefield
If the creature is already monstrous when the monstrosity ability resolves, nothing happens
If you truly want the best of Saga decks, then Tom and Narci should definitely in in your short list for the 99, along with some Assassins Creed action from Sigurd