Blood Brotherhood (3.5e Spell)

''As each creature pours its blood into the bowl, you chant the incantation and the blood glows a soft red color. Then each creature drinks the blood.''

Mix blood from any number of creatures who each have a CR of 5 or less, then have each of those creatures drink some of the mixture. Creatures who just donate or just drink the blood without also doing the other thing are unaffected by this spell.

All affected creatures share a single hit point total, with current and maximum hit point values equal to the combined total of all participating creatures. Any affect that changes the health total of any creature in the group (such as damage, healing, or Constitution changes) changes this combined total. Immediately after the combined total current HP is reduced to 0 or less, the spell ends and each creature now has its own personal hit point total instead, with current health equal to the combined current HP value. For example, if the group is reduced to -3 from an attack, then the spell would end, leaving all the affected creatures at -3.

In addition, affected creatures can communicate telepathically with each other using any type of sensory data both creatures are capable of experiencing (so a Tremorsense creature can project Tremorsense feelings to other affected Tremorsense creatures, but not to creatures incapable of Tremorsense).

Creatures who somehow advance to have a CR greater than 5 are immediately removed from the group of affected creatures, subtracting their normal maximum HP from the current and maximum HP of the total, and returning to their normal HP, with full health.

Material Component: An ounce of blood from each creature. Creatures of tiny size or smaller take 1 point of damage from the blood loss.