[baqwuqso] Monsters in Lake Baikal

Large lakes are sometimes inhabited with cryptozoological monsters (Loch Ness Monster, Champ, Ogopogo).  (Also similarly of course, the ocean.)  Invent such a monster for Lake Baikal, which currently doesn't have one: as a very large, very deep, very old, fairly remote lake with a similar long thin shape as Loch Ness, there is plenty of room for imagination: it surfaces only once every million years to feed.

Currently only exists folklore of how the nerpa got there, so far from the ocean.