Eusebio's Multiplicative Gnolls

You take the flesh of an intelligent humanoid and feed it to one beast-type creature. If the creature is unwilling, it must have its mouth open and make a STR Save against your Spell Save DC. If it fails the save after one hour the beast becomes pregnant with three Gnoll Flesh Gnawers, this birth kills the beast, but the Gnolls are friendly to you and your allies, and take the same initiative as you in combat. After 24 hours, they no longer have loyalty to your party and go their separate ways.

At Higher Levels. You summon an additional Gnoll Flesh Gnawer for every spell slot above 6th.