Summoning Frenzy: Skeleton Evolution

One day hundreds of years ago, countless time and space rifts appeared on the earth. Dragons, monsters, demons, bugs, undead creatures, and elemental races invaded the earth. Human beings went to war with various races, and then entered the dark age. The young boy Bai Gu woke up and came to the end of the world hundreds of years later, and became a summoner. At the beginning, he summoned the most rubbish little skeleton. However, he has a system that can evolve and improve his summons. Evolve from a small skeleton to a skeleton warrior, skeleton archer, skeleton mage, skeleton knight, ghost bone assassin, lich, skeleton king, poison dagger thrower, skeleton knight, and bone giant.