Summon Unbound Dremora

 is a Novice-level Conjuration spell in. Casting it summons Valkynaz, a Dremora Lord, which must be defeated before Phinis Gestor allows the Dragonborn to purchase Master-level Conjuration spells, such as Flame Thrall.

Acquisition

 * Phinis Gestor provides the Dragonborn with this spell as part of the Conjuration Ritual Spell quest once the Dragonborn reaches level 90 Conjuration.

Bugs

 * 360: (Uncomfirmed) After you summon the Unbound Dremora for the last time before he gives you the Sigil Stone, once you complete the quest "Conjuration Ritual Spell" you may see him walking up the stairs to where you had to summon the Unbound Dremora for the quest. It will appear as if he's exiting through the door leading outside. If you follow him, when you go outside he will stay at the entrance of the door and appear "frozen" to the spot. Attacks and any type of banish daedra spells do not seem to work on him.
 * There is a bug involving the use of followers in this quest. Followers tend to attack the Dremora immediately after being summoned, allowing no dialogue to pass and preventing the Dragonborn from re-conjuring it.
 * If the player loots the Dremora Lord after killing it, he/she will be unable to re-summon him and will have to load from a previous save to be able to continue the quest. Caveat: If the Dremora loses its weapons just before it disappears, the player may be able to use "Take Weapon" to retrieve it from the ground and cond continue the quest continued without bugs.
 * If a dragon appears after the Dremora has been summoned, it's possible that the Unbound Dremora would act like a character/creature and travel from the roof to wherever the dragon corpse is.