Xuthl has demonstrated only a few powers in his handful of appearances, but he is treated with respect by both sorcerers such as Thulsa Doom and demons such as the Devourer of Souls, which should be a good indication of his abilities. A simple ritual and incantation that even a middling sorcerer in the employ of Prince Irham could perform is sufficient to summon the demon lord. The ritual itself involves the combining of blood and some type of root along with the utterance of the phrase "Xuthl comes!". Xuthl appears as a pillar of living flame with an amused face of darker flame within. In at least one instance Xuthl promptly absorbed the sorcerer summoning him, spitting out his blackened bones a moment later. This implies that summoning Xuthl is not the same
as commanding him. Xuthl however commands lesser demons such as the Shedu and is not averse to loaning them out to others on "a favor for a favor" basis. Xuthl appears to not require summoning to manifest upon the mortal plane of existence if he wishes and has no trouble blasting ordinary humans into burnt bones and bloody gobbets of meat. Xuthl assisted Thulsa
Doom' s scheme to destroy the Devourer of Souls not for a return favor, but because Thulsa Doom thought it was in both their interests to do so and it amused Xuthl to do so.