Mono-Blue Terror is almost entirely blue with no artifacts, so Red Elemental Blast is excellent here, countering Counterspell, Tolarian Terror, and Cryptic Serpent or destroying a resolved Delver of Secrets. Electrickery's overload mode deals 1 damage to each opposing creature, which is enough to kill an unflipped Delver of Secrets (1/1) and any 1-toughness Faerie-type threats they might have. Thraben Charm comes out since its graveyard-exile mode does nothing against a deck with no real graveyard payoffs beyond cost reduction it can't stop that way, and its damage mode is often overkill. Bitter Reunion is trimmed slightly to make room, since proactive disruption matters more than extra filtering against their tempo-permission plan.