Izzet Delver mixes red threats and burn like Lightning Bolt, Dragon's Rage Channeler, and Cori-Steel Cutter with blue payoffs like Murktide Regent, which grows off the instants and sorceries in their graveyard. Hydroblast is live against their red cards, countering or destroying Lightning Bolt, Unholy Heat, Dragon's Rage Channeler, or a Cori-Steel Cutter Equipment, but it does nothing against blue cards like Murktide Regent, Daze, or their cantrips. Surgical Extraction has to target a card already in a graveyard, so it can't stop a Murktide Regent or Dragon's Rage Channeler on the stack. Once one of them hits the graveyard, it exiles every copy from the graveyard, hand, and library, and it can also strip a named piece of delve fuel such as Lightning Bolt. Thoughtseize is weaker here because tempo decks punish the 2-life loss and the tempo deficit, so we cut it. We also trim some Fatal Push: it can never kill Murktide Regent, which has mana value 7 since delve only reduces the cost paid, but it still handles Dragon's Rage Channeler and Monk tokens, so we keep one copy.