For 10 points, identify this animal whose form was adopted by both Ra's protector Mehen and Ra's enemy Apep.
One figure who took the form of this creature was said to hang out at the mountain Bakhu and was sometimes depicted being decapitated by the Great Cat of Iunu at the foot of a sycamore tree. Other adopters of this form include Kauket, the female form of the darkness god Kuk, and a two-headed god who guarded Duat named Nehebkau. One text claims that a god who took this form first appears at the seventh hour; that god is also the namesake of a segmented (*) board used in a namesake marble game. Possibly the best-known of these creatures was married to the fertility goddess Taweret and is fought off by Set, who sits in the helm of the solar barque. For 10 points, identify this animal whose form was adopted by both Ra's protector Mehen and Ra's enemy Apep.
One figure who took the form of this creature was said to hang out at the mountain Bakhu and was sometimes depicted being decapitated by the Great Cat of Iunu at the foot of a sycamore tree.
{snakes} [or {serpents}; {even} accept {dragons} since {apparently Apep} is {sometimes depicted} as one]