Players have found plenty of combos to enable with Chatterfang, whether to get them miles ahead of their opponents or to outright win the game
This version of Atraxa lets you play plenty of colors to do different stuff, and it gives you a free proliferate every turn
If you mean 'challenging' other characters, or glimmers, in play Steel and Ruby are good at challenging and can get benefits for banishing opposing characters during challenges
Its good when youre behind, its good when youre ahead, its good when youre at parity and its good in the developing stages of the game
But they are very reliable ways to pull ahead over the longer games of Magic which Final Fantasy creates
Things are better with Jens on your side, and there are not many cards that can create that wince without being very good