Thunderstom is a skill in Ghosts 'n Goblins Resurrection, unlockable as soon as Arthur gets his first Umbral Bee alongside Firewall I.
When casted, a thunderbolt will come down on Arthur and shock any enemy horizontally in the vicinity of Arthur himself.
Once Doppelganger I has been equipped, Arthur can learn Thunderstorm II for 4 Umbral Bees, which adds a diagnal version of the shock as seen in the orginal version
When Emboulden II is unlocked, Arthur can unlock Thunderstorm III for 20 Umbral Bees, which adds a third shock in an X pattern, and a short period of raining holy water, which damages Boss monsters, and is the only spell that could be able to do so.