Complex sentence: He gave Heracles the lion's invincible pelt to wear as a cloak, but warned Heracles that the tasks set for him would become increasingly difficult and then King Eurystsheus sent Heracles off to complete his next, more difficult quest.
Split into simpler sentences: He gave Heracles the lion's invincible pelt to wear as a cloak, but warned Heracles that the tasks set for him would become increasingly difficult. He then sent Heracles off to complete his next, more difficult quest.