Evo Magneto (Blue)

If you have a base arms equipped, transform it into this, then equip this.

When this defends, you may destroy a card under it. If you do, gain control of target item with cost 1 or less controlled by the attacking hero.

Temper

Rulings

From the Heavy Hitters release notes

If there is no attacking hero (e.g. you’re defending against an ally attack), this will trigger but no layer will be put onto the stack because there is no valid target (no attacking hero means no item controlled by the attacking hero).
When you defend with (and trigger) Evo Magneto, you must choose a target item for its triggered effect when the triggered layer is put onto the stack.
You choose whether to destroy a card under Evo Magneto when the trigger layer resolves.
There is priority between choosing the target an item (i.e. putting the layer on the stack) and resolving the triggered layer. There is no priority between choosing to destroy a card under Evo Magneto and gaining control of the target item.

Keyword notes

Temper - Temper is a new keyword that exists on equipment in Crucible of War. Usually high in defense, Temper equipment presents a choice when it is down to 1{d}, of whether to defend with it one last time and see it destroyed, or save it to use for its ability.