The Magic-Sucker is a weapon that can temporarily take away somebody's magic. It makes its' first (and only) appearance in The Dying of the Light, where it exists only in the alternate dimension ruled by Mevolent.
When Mevolent encounters Darquesse he uses it on her. She then after losing the fight leaves the dimension. Nefarian Serpine demands that they retrieve it in exchange for him breaking out Skulduggery Pleasant and Erskine Ravel out of prison. When Mevolent then attempts to use it on Valkyrie Cain, it has no effect, as Darquesse took all of Valkyrie's magic. He discards it, allowing Emmett Peregrine to pick it up and teleport them back to Serpine. However, Lord Vile attacks, and the Magic-sucker breaks in an explosion that kick-starts Valkyrie's Surge.