Jules needed Eren's presence as an anthrope to open purgatory.
A ranker's purgatory, or just purgatory, was similar to a ranker's utopia in many ways. It was a separate dimension created by S-Rank entities in their final stage of the rank to choose their successor by testing their mettle.
But unlike the ranker's utopia, a purgatory was created by heretic rankers of their time now known as cultists. A purgatory was much more brutal and dangerous to explore than a utopia. Purgatory exploration usually results in heavy casualties.
But these risks carried substantial rewards. A purgatory usually contained the S-Rank entity's complete inheritance. High-ranked heretic rankers of their times would rob and plunder all the riches they could find. And then they would dump all their loot in the separate dimensions they created.
Your gift is the motivation for my creation. Give me more motivation!