To say hastur is to invite his wrath for he has a large chance of hearing. He will at first send his servants, the dreaded batlike byakhee. If they are defeated he himself will come to destroy the blasphemer. A way of jokingly bringing their friends or seriously bringing their foes' doom was by saying "My dying words are hastur, hastur, hastur..." and they would say his name until Hastur hears it.
Hastur is the half brother of Cthulhu, though he has no special love for his half brother, for Hastur is the master of Air, and Cthulhu is the master of Water, and they are opposing elements. Which is intriguing as this is a departure from classical elemental theories.
A master manipulator, he is no less powerful than his brother and has the ability to laugh off nuclear weapons, bring madness with ease, and has mastered every spell in existence, including the spell to summon Azathoth, which is quoted as having the ability to fry an entire universe with incredible ease. He also has the power of shapeshifting, having taken on the form of a human dressed in yellow garments, a vaguely octopus like creature, a gigantic reptilian humanoid with tentacles writhing all over it's body, a pulsing blob of writhing tentacles, and worse.