Elemental Servants

Elementals can be bound by magic to serve as servants.
They can be summoned by a Summon Elemental spell of the appropriate level. When bound, Elementals have a bracer on each arm to show they are bound, with the sigil of the one who bound it clearly visible.
Elemental Servants cannot be used for combat. If forced, they will make one attack, and then the summon bind breaks, and they disappear, returning to their Elemental Plane.
Rumors persist of bound elemental warriors, but none have been publically acknowledged.
Elemantals which are Unbound are dangerous monsters.