Talk:Gameplay/@comment-11454852-20131205205529/@comment-4292163-20131206024932

I suspect that you can only use cards from your flag's world (like you suggested elsewhere Tyrant), but that we'll eventually get flags that let you use multiple worlds (presumably with some sort of drawback).

After all, if they just wanted to restrict us to one world, they could just make it a rule. That they would introduce an entire card type for it instead, suggests that flags are going to serve a larger purpose. Flags with special effects are inevitable, and multi-world flags is one of the most obvious effects.