Polarities Mod/Dipole Staff

The Dipole Staff is a Hardmode summon weapon that drops from. When used, it spawns miniature versions of Magneton and Electris, known as Magnetomini and Electrimini respectively, which follow the player and attack enemies. They move similarly to the Polarities, moving to keep a straight line between them with the player in the middle as they move. Magnetomini fires a constant barrage of magnetic rockets that home in on nearby enemies, while Electrimini will fire a laser beam every few seconds that deals rapid damage, but it cannot change its angle while firing so it's likely to lose its target if the player moves. Neither of these attacks can pierce through terrain, likely reducing their damage output significantly if the player is standing on solid ground.

Trivia

 * The Polariminis use the same sprites as the dropped by the Polarities.