This is the Moat Lurker HS Card. This card is part of the One Night in Karazhan adventure being released on the 11th August.
The card reads: Battlecry: Destroy a minion. Deathrattle: Resummon it.
This is an interesting effect. You can use it on your own minions to basically restore their health when they resummon. Or, you can use it on an enemy minion that you need off the board until this minion dies as a tempo gain.
It looks over-costed at first glance. 6 mana for a 3/3 is a steep cost, and the effect doesn’t seem to justify the cost. We will have to see how it works when it’s released and we can play-test it.