[Taqwus]

I haven't experimented much with blood battle magic, but there's also Leech and Hellbind Heart.

Incidentally, Zen's 'conceptual balance' mods alter some of the blood spells; IIRC, the Sabbath spells no longer require blood slaves, for instance, which makes Blood's equivalent of Communion much easier to achieve. In addition, the removal of Gift of Reason gives Hellbind Heart (blood) and Charm (nature) an advantage over Enslave Mind when used on commanders of interesting ability; the latter (now irreversibly due to lack of GoR) turns the victim into a normal unit sans equipment (lost even if GoR is allowed) and magic (formerly possible to re-roll via GoR).

Blood has a reputation as a ritual summoning/construction school, however, and there it's rather strong even if it's a bit lacking in massive area/massive damage spells that the elemental schools tend to have.