Dark Wisdom

You enhance your magical knowledge by performing a series of ritual sacrifices. As part of the spell, you must ritually kill creatures, except constructs or undead, in increments of 5. For every increment higher than one, the casting time is increased by another 4, and you need another spellcaster of your class to be present in assisting you. Once completed, it is unable to be cast for another month, but the numbers you now know is increased by every increment of 5 sacrifices you made.