Miriko, the Living Leyline

Flying, hexproof, defender

For each pair of opponents, create a zone between them called "Combat Zone". Players can only be attacked by creatures in a shared Combat Zone, and creatures in a Combat Zone can only block creatures controlled by a player who shares the same zone.

At the beginning of each player's end step, there is an additional phase called Movement. During the Movement Phase, the active player may move any number of creatures they control to or from a Combat Zone.