Brokkos, Apex of Forever

Mutate appears on some creature cards. It represents a static ability that functions while the spell with mutate is on the stack. “Mutate [cost]” means “You may pay [cost] rather than pay this spell’s mana cost. If you do, it becomes a mutating creature spell and targets a non-Human creature with the same owner as this spell.” Casting a spell using its mutate ability follows the rules for paying alternative costs (see 601.2b and 601.2f–h).

As a mutating creature spell begins resolving, if its target is illegal, it ceases to be a mutating creature spell and continues resolving as a creature spell and will be put onto the battlefield under the control of the spell’s controller.

As a mutating creature spell resolves, if its target is legal, it doesn’t enter the battlefield. Rather, it merges with the target creature and becomes one object represented by more than one card or token (see rule 727, “Merging with Permanents”). The spell’s controller chooses whether the spell is put on top of the creature or on the bottom. The resulting permanent is a mutated permanent.

An ability that triggers whenever a creature mutates triggers when a spell merges with a creature as a result of a resolving mutating creature spell.

A mutated permanent has all abilities of each card and token that represents it. Its other characteristics are derived from the topmost card or token.

Any effect that refers to or modifies the mutating creature spell refers to or modifies the mutated permanent it merges with as it resolves.

Trample is a static ability that modifies the rules for assigning an attacking creature’s combat damage. The ability has no effect when a creature with trample is blocking or is dealing noncombat damage. (See rule 510, “Combat Damage Step.”)

The controller of an attacking creature with trample first assigns damage to the creature(s) blocking it. Once all those blocking creatures are assigned lethal damage, any excess damage is assigned as its controller chooses among those blocking creatures and the player, planeswalker, or battle the creature is attacking. When checking for assigned lethal damage, take into account damage already marked on the creature and damage from other creatures that’s being assigned during the same combat damage step, but not any abilities or effects that might change the amount of damage that’s actually dealt. The attacking creature’s controller need not assign lethal damage to all those blocking creatures but in that case can’t assign any damage to the player or planeswalker it’s attacking.

Trample over planeswalkers is a variant of trample that modifies the rules for assigning combat damage to planeswalkers. The controller of a creature with trample over planeswalkers assigns that creature’s combat damage as described in rule 702.19b, with one exception. If that creature is attacking a planeswalker, after lethal damage is assigned to all blocking creatures and damage at least equal to the loyalty of the planeswalker the creature is attacking is assigned to that planeswalker, further excess damage may be assigned as the attacking creature’s controller chooses among those blocking creatures, that planeswalker, and that planeswalker’s controller. When checking for assigned damage equal to a planeswalker’s loyalty, take into account damage from other creatures that’s being assigned during the same combat damage step, but not any abilities or effects that might change the amount of damage that’s actually dealt.

If an attacking creature with trample or trample over planeswalkers is blocked, but there are no creatures blocking it when damage is assigned, its damage is assigned to the defending player and/or planeswalker as though all blocking creatures have been assigned lethal damage.

If a creature with trample over planeswalkers is attacking a planeswalker and that planeswalker is removed from combat, the creature’s damage may be assigned to the defending player once all blocking creatures have been dealt lethal damage or, if there are no blocking creatures when damage is assigned, all its damage is assigned to the defending player. This is an exception to rule 506.4c, and it does not cause the creature to be attacking that player.

If a creature without trample over planeswalkers is attacking a planeswalker, none of its combat damage can be assigned to the defending player, even if that planeswalker has been removed from combat or the damage the attacking creature could assign is greater than the planeswalker’s loyalty.

Multiple instances of trample on the same creature are redundant. Multiple instances of trample over planeswalkers on the same creature are redundant.