The Ancient Scorpos - Beast of Legend is a Scorpos hero monster found in a cave in the Wadjet Canyons. He's part of the side quest The Beast of Legend and needs to be killed in order to complete the quest. He belongs to the Insectoid class.
The amount of experience gained depends on your character's level (like Hero Monsters).
The Ancient Scorpos is an extremely fast and quite durable melee fighter. His attacks are moderate to strong. He uses three attacks: A regular melee attack, a ranged poison attack (slow moving poison projectile, also slows down target) and a tail attack. When getting close to him, he often casts an aura spell that buffs himself and any nearby monsters. Occasionally he also uses a horn to heal and bolden himself and nearby allies.
While the Ancient Scorpos might be somewhat durable, he should prove less trouble than Scarabeus (the giant scarab in the library). You might want to dispose of any other monsters first, that could take advantage of the aura effect. Boosting resistances against poison and slowdown might also be helpful. Due to his high movement speed it is quite difficult to escape him.