Shoggoth have no concrete shape. They consist of a sticky black substance that can form limbs and other structures at will. They can even change sapience level, depending on what they form as. It is not known how they perform this process. But no matter what shape they take, they are always black.
DietEditShoggoth completely wrap themselves around other lifeforms for a few minutes. When the Shoggoth unwraps itself, the prey is gone. It is presumed that it is absorbed into the creature.
HistoryEditLittle is known of these lifeforms. When they speak, they have mentioned worshipping "Elder Gods".