The Battlefield

Hullbreaker Horror
Mana Vault
AI DraftFeb 26, 2026

Hullbreaker Horror + Mana Vault

Overview
Hullbreaker Horror's triggered ability can return a Mana Vault either as a nonland permanent (if Mana Vault is already on the battlefield) or as a spell on the stack (if Mana Vault is currently a spell on the stack) — but only if Hullbreaker is already on the battlefield when you cast a spell to create the trigger. Abilities printed on Hullbreaker function only while it's on the battlefield ; targets for triggered abilities are chosen when the ability is put on the stack and checked again on resolution .
Step 1
Scenario A — Mana Vault is a permanent and Hullbreaker is already on the battlefield: You cast any spell. Hullbreaker’s triggered ability is put on the stack and you may choose to target the opponent's Mana Vault (a nonland permanent) as it is a legal target and . When the trigger resolves it returns Mana Vault to its owner's hand, moving that permanent from the battlefield to the owner's hand .
Step 2
Scenario B — Opponent cast Mana Vault and it is currently a spell on the stack, Hullbreaker is on the battlefield: Opponent casts Mana Vault (it is a spell on the stack). In response you cast a spell (while Hullbreaker is on the battlefield). Hullbreaker’s triggered ability is put on the stack and you may target the Mana Vault spell on the stack as a "target spell you don't control" and . When the trigger resolves it returns the Mana Vault spell to its owner's hand (removing it from the stack) .
Step 3
Scenario C — Opponent cast Mana Vault as a spell, you cast Hullbreaker in response (Hullbreaker was not already on battlefield): You cast Hullbreaker (it is a spell on the stack). Hullbreaker’s static/triggered ability that says "Whenever you cast a spell..." does not function while Hullbreaker is on the stack because it's a permanent ability that only functions on the battlefield . Therefore the Hullbreaker you just cast cannot be used to return the opponent’s Mana Vault spell that is already on the stack.
Resolution
If Hullbreaker Horror is on the battlefield and you cast any spell, its triggered ability may target and return an opponent's Mana Vault that is a nonland permanent to its owner's hand when the ability resolves and . If an opponent has just cast Mana Vault and it exists as a spell on the stack, and Hullbreaker is on the battlefield when you cast a spell, the trigger may instead target that Mana Vault spell and return it to its owner's hand (removing it from the stack) and . If you cast Hullbreaker as a spell in response to an opponent casting Mana Vault, Hullbreaker is not yet on the battlefield and therefore its “Whenever you cast a spell” ability does not exist yet, so it cannot be used to return that opponent's Mana Vault spell .
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