Ghostly Flicker, which back in the day enabled some sick combos, including the ability to endlessly recur it with Archaeomancer and some other permanent with an advantageous 'enters the battlefield' effect. But even without such a combination, this card has the potential to be quite strong, allowing you to sidestep removal, escape from negative Auras, or just get double mileage out of any ability that activates upon summoning.
So just how many creatures are there in the format that have advantageous 'enters the battlefield' effects? Turns out, there's plenty - 81, to be exact. Looking to recur Auras? Try Auramancer or Ironclad Slayer. Want to amass a bunch of tokens? Try Eyeless Watcher. Wanna get even more value out of your Allies? Now you can! Return multiple creatures from the Graveyard? Midnight Scavengers is the man for the job. Almost any strategy you're playing can be enhanced by successfully casting this card.
And while you can't actually pull off the same combo with it as you could with Archaeomancer, you can still use a 'turned face up' Monastery Loremaster to return Displace to your hand, allowing you to get even more value out of it.
However, it will be interesting to see if the Sultai Control deck which was so dominant last season will transform to make the best use out of Displace, since on the surface it doesn't have very many creatures that have a powerful ability when they enter the battlefield. Sure, you can draw another card off Elvish Visionary or another Land off of Pilgrim's Eye, but neither of those are particularly impressive. On the other hand, squeezing an additional Exploit off of Vulturous Aven seems quite strong, assuming you have the sacrifice outlet to support it.
In any case, there should be a great deal of strong combinations you can pull off with Displace, and I can't wait to see what some of our more innovative deckbuilders come up with!