It cripples enchantress decks and many non-green EDH lists that rely on talismans and signets for acceleration
By repeatedly Escaping Lion's Eye Diamond for mana and recasting Wheel, you can cycle through your entire deck, build an enormous Storm count, and dig toward whichever win condition finishes the game
Being in mardu also gives you access to Ruinous Ultimatum, one of the best board wipes that can be easily cast with an excess of Treasure for mana
With the ability to buff your entire board with +1/+1 counters and give your creatures vigilance for as long as he sticks around, Ajani, the Greathearted is an absolute powerhouse of a cat whether hes played early or late game
If an object has no controller (such as a card in a graveyard), its owner is considered its controller for this purpose.
And what formats do we expect them to excel in