Ultroloth

Ulthroloths are the strange, enigmatic rulers of the yugoloths. These creatures hold sway over their underlings by the force of their will and their reputation for cruelty.

These ruling yugoloths appear as faceless humonoids with large eyes that resemble fire-opals. They have dark gray skin and typically wear flowing capes or cloaks.

They communicate using telepathy.

Combat
Ultroloths, though evil, are cerebral and reserved. They rarely enter combat. Their physical attack consist of two hand strikes, whilst their touch inflicts energy damage.

They can be found carrying weapons, too. They are fond of swords and great pole-arms.

Their gaze has the power to fascinate, as the spell hypnotic pattern.

No attack of a nonmagical nature may affect an ultroloth. They are harmed only by weapons of magic.

They have infravision and are never surprised.

Habitat
None of the lower plane mercenaries would dare to disobey an ultroloth for fear of the punishment. Even non-yugoloths dwelling in the lower planes will steer clear of them, fearing their powers.

Note that the actual power of the ultroloth is not all that much greater than the other of their kind. However, no yugoloth of lesser status knows the capabilities of their rulers.

They are of an unknown quantity, and thus greatly feared.