IMPORTANT UPDATE: This article has been updated as of the prerelease of Magic 2014 on July 13; Please refer to the revisions below.
This was briefly explained in the Battalion mechanic blog entry last week, but it’s still a common question, so I’m making it as a bonus entry all to itself!
All the triggered abilities labeled with the Battalion ability word have the same trigger condition: “Whenever
and at least two other creatures attack,.”
To understand why Geist and its Angel can’t both count for Battalion’s purposes, you need to know what “attack” truly means in this context. For a creature to “attack” it has to “be declared as an attacking creature during the turn-based action of declaring attackers at the start of the declare attackers step.” That’s obviously very clunky and verbose, so when the Magic team realized that they could just say “attack” and have it mean the same thing, they went with that!
So, if you want your Battalion ability to trigger, you need to actually declare three creatures as attackers. This could be Geist, Medic and any other creature you control (that isn’t sick) as you declare attackers. Once attackers are declared, the game checks for triggers, and sees that two abilities had their trigger conditions met: the Medic’s Battalion ability, and the Geist’s “attacks” ability.
However you stack those triggers, you’ll end up with an Angel that will be indestructible along with your other creatures.
If you put the Angel trigger on top of the stack, it will appear for a short time as a creature that is NOT indestructible while the Medic’s trigger is waiting to resolve, but that usually doesn’t matter too much. If you put the Medic’s trigger on top of the stack, it will resolve and change the game rules for you with a temporary rule that says “Creatures you control are indestructible this turn.” Since this isn’t adding any abilities to the creatures themselves, the set of affected creatures isn’t locked in, and anything that enters under your control afterwards (e.g., the Geist’s Angel token) will also be indestructible this turn.
If you attack with only the Geist and the Medic, then the game will check and see that only one ability triggered from declaring attackers, because only two creatures attacked. After the Geist’s Angel is created as an attacking creature (but isn’t considered to have “attacked”), you’re well past the point where Battalion would have triggered at all.
Today’s Rules Tip written by Josh Stansfield
Only a slight update on this one! Everything Josh wrote about Battalion and Geist still applies, that’s all just fine. What changed with M14 is that “Indestructible” is now an ability. Similar to the change with Rootborn Defenses, Frontline Medic will only make things Indestructible if they’re around to see that trigger resolve. While you could previously stack the triggers however you wanted and end up with an indestructible Angel, there’s now only one way to do that: have Geist’s trigger make a little Angel buddy for him BEFORE Medic’s ability makes your creatures indestructible. If you do it the other way around, she’s not present to have the ability granted to her and will remain tragically destructible for the remainder of her short lifespan.
Today’s Rules Tip updated by Trevor Nunez