Magmaul

''"The MAGMAUL, powered by a hyperstatic hydrogen core, fires cohesive projectiles of SUPERHEATED MAGMA." -Metroid Prime: Hunters Logbook Entry'' The Magmaul is the bounty hunter Spire's affinity weapon. It is a magma grenade launcher with a large splash radius. The grenades bounce off walls and objects and explode after three seconds. When charged, it produces a larger and more damaging projectile with a much greater splash radius. If it is used by Spire, it has an even larger splash and sets nearby enemies ablaze. However, if Spire burns an enemy hunter that is very close to him, Spire will get burned too.

The Magmaul is used to open the Orange Force Fields in Alinos and the Orange Blast Shield in Arcterra.

Samus acquires the Magmaul after defeating the Fire Spawn at Alinos.

Mutiplayer Role
The Magmaul is the best weapon to use against anyone in alt form. It has a decent range so you can attack from a distance, and the splash damage gives you a slight margin for error if your aim is off.