Invasion of Muraganda // Primordial Plasm

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.

Damage dealt to a battle causes that many defense counters to be removed from it.

You can choose only a creature you control as a target for Invasion of Muraganda’s enters-the-battlefield ability.

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.

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.

A creature that loses all abilities because of Primordial Plasm’s ability (slurp) may later gain abilities.

If the creature affected by Primordial Plasm’s ability (slurp) had an ability defining its power and/or toughness, that base value will become 0. In many situations, having a base toughness of 0 would be a problem, but Primordial Plasm’s ability (slurp) helpfully provides +2/+2, so the creature should survive.

As a Siege enters the battlefield, its controller chooses an opponent to be its protector.

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 can be attacked by all players other than its protector. Notably, this means a Siege’s controller can attack it.

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.

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.

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.”

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.

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 the creature you control is an illegal target as the ability tries to resolve, you won’t put a +1/+1 counter on it. If that creature is a legal target but the other creature isn’t, you’ll still put the +1/+1 counter on the creature you control, but neither creature will deal or be dealt damage.