Rule 462.2

In Modes of Play with more than two players, Battlefields with Staged Combats or Combats in Progress are Invalid to be chosen as a location to play one or more Units by a player not involved in that Combat by any means.

• 462.2.a If an effect would require a Unit be played to a Battlefield with a Staged Combat or a Combat in Progress, where the…
• 462.2.b Any subsequent reference to "here" in the corresponding effect is reassigned to the Controller's Base, where the Unit…

Official Core Rules