Sieges each have an intrinsic triggered ability. That ability is “When the last defense counter is removed from this permanent, exile it, then you may cast it transformed without paying its mana cost.”
Invasion of Mercadia // Kyren Flamewright
If a non-battle permanent that is already on the battlefield become a copy of a Siege, its controller chooses one of their opponents to be that battle’s protector. However, it will most likely be put into its owner’s graveyard because it has no defense counters (see below).
If a battle that’s being attacked somehow stops being a battle, it is removed from combat. Similarly, if its controller changes in the middle of combat, it is removed from combat.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Cristi Balanescu
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
