Final answer:
The agreement between Pelias and Jason was for Jason to retrieve the Golden Fleece in order to gain kingship.
Step-by-step explanation:
The agreement between Pelias and Jason is a part of Greek mythology and is commonly known as the Golden Fleece quest. Pelias, the king of Iolcus, promised to give up his throne to Jason if he could retrieve the Golden Fleece from the land of Colchis. Jason agreed to the terms and assembled a group of heroes known as the Argonauts to accompany him on the journey.
The primary purpose of this agreement was for Jason to prove his worthiness as a hero and gain kingship. The Golden Fleece was a symbol of power and prosperity, and retrieving it would establish Jason's position as the rightful ruler of Iolcus.
Throughout the quest, Jason and his companions faced various challenges and obstacles, including battling mythical creatures and dealing with the gods' interference. Ultimately, Jason succeeded in obtaining the Golden Fleece and returned to Iolcus, fulfilling the agreement with Pelias.