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Python is the overarching antagonist of the Trials of Apollo series by Rick Riordan, which is a sequel series to Percy Jackson and Heroes of Olympus. Based on the mythical creation of the same name, he is a malicious deity who seeks to control the oracle at Delphi and manipulate the future. He is the arch-nemesis of Apollo.
Python was born to the deity Gaea. He took control of the Oracle at Delphi. When Leto came here looking for a place to give birth after Hera cursed her, Python chased her out. Apollo defeated him and was able to take control of the Oracle.
Blood of Olympus
Gaea resurrected Python to take the oracle at Delphi back. Apollo failed to stop this, partially due to the fact that his Greek and Roman aspects were in conflict.
The Hidden Oracle
Python manipulated the Triumvirate, particularly Nero, to take control of all of the oracles. He told Nero to destroy the Grove of Dodona.
The Burning Maze
Python was furious that Apollo was still alive. He argued with Nero about how to proceed with their plan to destroy Camp Half-Blood and Camp Jupiter.
The Tower of Nero
Python took control of the Oracle and possessed Rachel Dare to manipulate the future. Apollo found out that Python was manipulating Nero in a similar way that Nero was manipulating his foster children. After Apollo killed Nero, Nero's godly energy went to Python. Apollo then confronted Python. Python started to issue a prophecy saying that Apollo would fall. However, Apollo stopped him from completing it, and the two fell into Tartarus, which fulfilled the partial prophecy. The two landed at the edge of Chaos. Apollo managed to defeat Python, who fell into Chaos and was destroyed for good this time.
As Apollo's nemesis, Python is extremely powerful. In fact, Apollo himself admitted he needed to use all his strength and divine power to defeat the monster, and even after Python's defeat, fear of the serpent still haunts the Olympian god. After his resurrection by Gaea, Python is shown to be able to absorb the power of the Triumvirate when they are killed, making himself more powerful each time. After Python's destruction, Python is revealed to have been so powerful that his poison was influencing the threads of the Fates which could've potentially given Python the power to end or prolong lives at his will.