Origins Main Set OGN-206/298 common Official FAQ
Back to Back
Card Text & Abilities
[Reaction] (Play any time, even before spells and abilities resolve.) Give two friendly units each +2 [S] this turn.
Official Rules FAQ & Clarifications
1 Official FAQ Q:
If a spell has multiple targets, like Back to Back, do I need to choose targets for all of them to put the spell on the chain?
A:
Yes. You must choose two different friendly units to play Back to Back, although it still resolves even if one or both of its targets are no longer valid when it resolves. This is also true for activated abilities that have multiple targets.
Source: Official FAQ: Origins FAQ →