Meld cards copying other meld cards
1. When the trigger resolves, they're exiled, and go back to being the Garrison and Battlements. In exile, the game sees the two exiled cards make a melded pair, and they'll return to the battlefield fused as the Writhing Township.
2. You exile all four cards. You then choose one Rats and one Scavengers to return, and they'll return fused as the Host. The other two cards remain in exile.
Nathan Long
Magic Rules NetRep