Rally – Whenever Hero of Goma Fada or another Ally enters the battlefield under your control, creatures you control gain indestructible until end of turn.
It's interesting that they're essentially keywording this mechanic for Allies, leading me to believe that it will appear on other creature types, as well, rewarding you for playing tribal decks. Making all of your creatures indestructible is pretty awesome simply because it allows you to attack indiscriminately. Being a 5-drop, though, it will mean that Allies will have to be pretty good for this to see play. It may just be a bit too slow.