Battle — Siege // Creature — Elemental
Battle — Siege
(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.)
When this Siege enters, it deals 3 damage to each creature and each planeswalker.
Creature — Elemental
Ward—Pay 2 life.
Whenever you cast a spell, this creature deals 2 damage to each opponent.
This triggers when the spell is cast, before it resolves. Even if the spell is countered, the cast trigger still resolves. Copies of spells are not cast, so they won't trigger this.
This card uses a replacement effect ('as [it] enters' or 'enters with') to modify how the permanent enters. This is NOT a triggered ability — it can't be responded to, and effects like Panharmonicon or Torpor Orb don't affect it.