Many creatures were able to create clones - the quality, purpose, and number of clones varied depending on the strength of a person, but this ability could not be called unique.
Among Undeads, many were able to summon shadow clones - to distract opponents, to escape, and to conduct stealth attacks. However, such clones, like many others, were completely weak and could not convey even 1/1000 of the original.
However, sometimes clones could be quite strong opponents, a real weapon capable of forcing the enemy to use resources to destroy them.
Gael was a special case, as it was a waste of energy to use clones against such an opponent. After all, no matter how strong the clones were, they couldn't withstand the swing of his sword that could cut through anything.
It was obvious to everyone, as well as to Ereg, but that didn't stop him from using clones because they were different from everyone else.