Answer
Ptolemy, the ruler of Egypt, played a pivotal role in Seleucus' return to Babylon. After Seleucus was defeated by Demetrius and Lysimachus, he fled to Egypt for refuge. Ptolemy welcomed Seleucus and provided him with financial and military support. With Ptolemy's assistance, Seleucus was able to regain control of Babylon and re-establish his kingdom.