In Finnish mythology, Iku-Turso was a malevolent ocean deity who took the form a terrible sea monster. Due to the vagaries of language, it is unclear whether he (?) had the shape of a colossal walrus or a giant terrible inkfish (i.e. an octopus). Contemporary Finnish artists apparently see no reason he can’t be both and the internet has some amazing and disturbing images of the dark god of the depths.
Not only was Iku-Turso’s appearance formidable, but he seemingly had powerful and weird magic—a sort of divine antagonistic surrealist. The god makes a typically bizarre appearance in the Kalevala, the great mythological epic of the Finns (which Ferrebeekeeper has already visited—to tell the dark story of Lemminkäinen and the Swan of Tuonela). In the second canto, the god rises from the depths and burns a huge hay stack. From the cinders grows an oak so large that it threatens to blot out the sun and moon—and so the tree must be cut down. Later in the epic, Inku-Turso is enlisted by the goddess of the North (the witch Louhi) to prevent the theft of the powerful magical artifact Sampo. However one of the sorcerers seeking Sampo was too powerful for even a bizarre walrus/octopus sea god to stop. Poor Inku-Tursu ended up magically cursed to haunt the bottom of the ocean.
The dark god has made few appearances since then, but I imagine a Finnish epic about exploring the abyssal plains would be exceedingly exciting! In fact that sounds great for all sorts of reasons! Could some of you Finnish bards get busy and make it happen?