Volcano Hellion enters the battlefield, triggering itself.
Holding priority, activate General's Regalia by paying 3, choosing to redirect the next damage Volcano Hellion does to you to Spitemare instead.
Resolve Volcano Hellion's ability, dealing an arbirarily large amount of damage to Spitemare.
Spitemare triggers, dealing an arbitarily large amount of damage to target opponent.
This clever setup harnesses Volcano Hellion's self-inflicted damage trigger to turn your own life total into a lethal weapon. By using General's Regalia to intercept the damage that Volcano Hellion would normally deal to you, you safely redirect that massive blow straight into Spitemare. That incoming damage immediately triggers Spitemare's ability, letting you channel the entire arbitrarily large amount directly at your opponent's face to close out the game in one fiery sweep.