457.2. 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,
457.2.a. If an effect would require a Unit be played to a Battlefield with a Staged Combat or a Combat in Progress, where the controller of the played unit is not a participant, instead the Unit is played to its controller's Base.
457.2.b. Any subsequent reference to "here" in the corresponding effect is reassigned to the Controller's Base, where the Unit was played. Any further effects that may be invalidated are invalidated as if the effect was mistargeted. See rule 355.6. Targeting for more information on Mistargeting.