[casthaven]Gyre Sage[/casthaven]
If it's a likely hit for Standard or Modern but a swing and a miss for formats like Commander and multiplayer, then it's not here
Other cards, like Hedron Archive, are perfectly acceptable in a non-Green deck, but we have plenty of better alternatives at the same budget range, like Explosive Vegetation
(Artifacts, legendaries, and Sagas are historic.) The second mode of What Must Be Done cares about what the characteristics of the returned permanent will be when it's on the battlefield, taking into account static abilities that would change its types
In the early game it's just a five-mana Damnation, and in the mid-game it's an okay sweeper with a few dorks, later you can play around it and really push the board your direction
You can check out the cards from the Warhammer 40,000 Commander decks in the Card Image Gallery