Guardians of the Galaxy: Vol. 2 revealed that Celestial being Ego was Star-Lord's father. This explained why Star-Lord could hold an Infinity Stone in his hand, and how he managed to survive the years he spent in space. Even so, it appeared in the end that he'd lost his powers when Ego died.
But did he really lose them?
Maybe not. Reddit user EvilBananaManRD recently shared that fans discovered an Easter egg indicating that the Star-Lord/Mantis connection may be deeper than we thought, and that Star-Lord's powers may have remained intact. Ego hints at this when he tells Quill about how he traveled from planet to planet in search of a mother for his child.
BananaMan added that the Celestial apparently hooked up with someone from Mantis' race. Check out the pic below:
We can assume that Mantis' empathic powers lie in her antennae and are a trait of her race, but that doesn't explain how she could put Ego – a Celestial and one of the most powerful beings in the universe – to sleep. Nor does it explain how she was able to subdue a Mad Titan armed with an almost-complete Infinity Gauntlet.
The Reddit user pointed out that she may have been able to accomplish such feats because she's Ego's child – and, to state the obvious, Star-Lord's sister.
If this is all true, Mantis didn't lose her powers when Ego died. Considering how powerful Thanos is, we can even say that her abilities were enhanced. This also means that there's more to Peter Quill than we originally believed.
Who knows? Maybe Star-Lord is even more powerful than any of us thought. He might even take on an essential role in defeating the Mad Titan in Avengers 4. We know…he faded out of existence. However, it's widely believed that he won't stay dead for long.