Shamans get a new cheap spell - Rebirth - allowing them "refresh" the health of their minions by sacrificing them first.
Rebirth's application is more than obvious - with Naxxramas centered around Deathrattle, this card will be an easy way to trigger such effect without losing the minion in the process. Rebirth [card]Cairne Bloodhoof[/card] to spawn a Yeti for 2 mana. Sacrifice [card]Sylvanas Windrunner[/card] to immediately steal a minion while keeping a 5/5 body on the board.
This will possibly incentivize Shamans to create more varying builds as right now the optimal decks of the class or more or less figured out.
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