Bloodghast An oldie but a goodie
Miara, Thorn of the Glade Miara, Thorn of the Glade needs elves to turn into card advantage, and when it does, is very effective
If the creature this Aura is attached to leaves the battlefield or stops being a creature before the activated ability resolves, Wingspan Stride will be put into its owner's graveyard as a state-based action before that ability resolves, and it won't be returned to its owner's hand
The card can also easily lock your opponent out of keeping a flier on the battlefield if you flip Atzal, since it can trade with any flier when you return it to the battlefield and then it goes right back to your graveyard to do it again
At best, players will have to call a time-out and look up the rules and agree on how to interpret them and put them into effect
This could cover that spot for extra threat coming from the sideboard