In the start of ep 3 you see a flashback of Gilgamesh the king when he was young. He looks and sounds exactly like Jil. The girl he rescues looks and sounds exactly like Kayaa. The dragon has a human face (probably the girl). The king kills the dragon, the girl appears, then both the dragon and girl sparkle away.
My guess is that it'll end like secret of mana, they kill the dragon, kayaa dies with the dragon, and the cycle will start over. The curse of druaga being that they have to repeat the climb every 100 years to save the world.