The best control ability in the game, Prison of Ice, and one of only two spells that damage the target instantly, Call Lightning (Cauldron of Blood being the other). Call Lightning is tactically superior against already moving targets; the most powerful damage spell by far is Firestorm
Prison of Ice
The ultimate defensive skill, shutting down all of its targets' abilities, no matter whether they are vampires, beasts, or humans.
Heart of Stone
Prevents against staking
Endure the Flames
Call Lightning
Can hit targets even if they are moving, but Firestorm is two to three times stronger against distant targets that will not move, or stay in one place to attack. No vampire clans start with this skill; it is only available as a tome (one in the single-player game)
No vampire Clans are given Blood Rituals, and it is not given in the course of the single-player game. Only one Tome exists in the Dark Ages, in the Tremere Laboratory )(Haus de Hexe 3) portion of the Haus de Hexe in Vienna. It is guarded by a Tremere Lord, just before the Arcanum piece at the end of the Lab.