Siege

Siege is a type of Battle, introduced in March of the Machine.
Sieges are placed on your opponent’s side, and transform into something when you deal enough damage to it.
==Description==
A siege is a military blockade and assault of a city or fortress with the intent of conquering by force or attrition. A siege occurs when an attacker encounters a city or fortress that refuses to surrender and cannot be easily taken by a frontal assault.
Sieges have the reminder text "As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed."
Every player except a battle's protector may attack it. Only a battle's protector may block creatures attacking it. Don't confuse protector for controller. You are able to attack battles that you control. This is the first time you've been able to attack your own permanents.
Any damage dealt to a battle causes that many defense counters to be removed from it. When the last defense counter is removed from a Siege battle, the battle is defeated and a triggered ability triggers. As this ability resolves, the battle's controller exiles it and then casts the back face from exile without paying a mana cost. The back faces are a variety of things; most of them are permanents, but there are also some sorceries.
==Rules==
==Example==
==Rulings==
*Battle is a new card type. Siege is a battle subtype. Sieges have some special rules that limit who can protect them, and they let their controller exile them and cast them transformed when they are defeated. All battles that currently exist are Sieges, but future battles may have different subtypes with different rules about who can protect them and what happens when they are defeated.
*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."
*As a Siege enters the battlefield, its controller chooses an opponent to be its protector.
*A Siege's controller can't be its protector. If a Siege's protector ever gains control of it, they choose a new player to be its protector. This is a state-based action.
*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).
*A battle's "defense" is displayed in the bottom right corner of the card. A battle enters the battlefield with that number of defense counters. If another permanent enters the battlefield as a copy of a battle, it also enters with that number of defense counters.
*Only creatures controlled by a battle's protector can block creatures that are attacking that battle. This means a Siege's controller can never assign creatures to block for it.
*A battle can be dealt damage and be target of spells and/or abilities that target "any target."*
*Damage dealt to a battle causes that many defense counters to be removed from it.
*A battle can be attacked by all players other than its protector. Notably, this means a Siege's controller can attack it.
*If a battle has no defense counters, and it isn't the source of a triggered ability that has triggered but not yet left the stack, that battle is put into its owner's graveyard. This is a state-based action. This doesn't cause a Siege's intrinsic triggered ability to trigger.
*Notably, if a Siege never had defense counters on it (perhaps because a permanent became a copy of one), it can't have its last defense counter removed. It will be put into its owner's graveyard. You won't exile it or cast the other face.
*If a token or a card that isn't represented by a transforming double-faced card becomes a copy of a Siege, it can't be cast as its triggered ability resolves. It will remain in exile. If it's a token, it will cease to exist the next time state-based actions are performed.
*If a permanent that is represented by a transforming double-faced card becomes a copy of a Siege, it will be exiled as that Siege's triggered ability resolves, then it will be cast transformed. Note that this applies only to transforming double-faced cards, not to modal double-faced cards that can normally be played using either face.
*In a multiplayer game, if the protector of a battle leaves the game and that battle is not currently being attacked, its controller chooses a new protector for it as a state-based action. If it is being attacked, its controller chooses a new protector for it once no creatures are attacking it. This means that it continues to be attacked and can be dealt combat damage as normal.
*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.
*Battles can't attack or block, even if one also becomes a creature. If an attacking or blocking creature somehow becomes a battle in addition to being a creature, it is removed from combat.
==References==