Kaisel

Kaisel is a wyvern in Solo Leveling, kept and ridden as a battle mount inside the Demon Castle, the hundred-floor instant dungeon of demons. It is large enough to carry a rider without difficulty and built entirely for the air, with black scales, a long tail, sharp teeth and curved horns, and it fights from above rather than on the ground, which makes it an awkward target for anyone without a ranged option. A mount at that level is not a beast of burden. It belongs to one of the castle's floor bosses, so meeting it in the air generally means meeting its rider at the same time, and dealing with the pair as a single problem.