"Shrouded in mystery", this creek will redirect every so often to flow uphill. When it does, coffins with dead bodies in them float in the water.
"The midnight gatherings were held at the Witches' Brew, an old tavern made entirely of twigs and mulch that sat in the middle of the creek like a giant beaver dam."
The tavern is destroyed by Alex when her magic causes to lift it high up in the air and then crash down to earth.
Later in Beyond the Kingdoms, the secret of the creek and the dead bodies is discovered: the witch Morina is draining human children for ingredients in her youth and beauty potions, and using the creek to discard the remains. Her magic makes the creek flow in the other direction.