They'd have to be immortal in order to be present at events in history that happened up to thousands of years apart. Despite the fact that Xena gets killed off in the end, so it must eventually wear off...
Well, it explains the strange reality-warping nature of the place, the strange distortion of various characters, and the spontaneous musical numbers. However, this is an older version of the Black Lodge before it was owned by the Little Man from Another Place, which is why he doesn't appear.
Xena ruined Callisto's life and Xena can fix it again! Well, at least that is what Callisto feels. So she torments Xena all the show until it works! at one of the final episodes, Xena really fix her and makes her an angel and send her to heaven!
- 'the Play's the Thing' applied Mel Brooks' "The Producers": promote a good opera and the sponsors earn a share of the profits; promote a bad opera, sponsors invest, the show fails, take the money and run.
- It is explicitly stated over and over that "Gabrielle's" story of Elijianity is boring, preachy and NOT entertaining at all.
- Classical Gabrielle was good at barding. She only lost the barding contest to Homer who is the super dooperest bard evah.
- Prophecy is Confirmed: seasons 5 & 6 were indeed boring, preachy and NOT entertaining.
- Gabrielle had zero emotions in season 5 and had some emotions in season 6.
- Eli commanded Gabrielle to have a skinhead Nazi hair-cut and use industrial strength hair Bleach.
- By season 6, Gabrielle hair regime was less severe and she was capable of emotions.
- More bleach = less emotions; less bleach = more emotions.
But that aside, the fact she manages to leap through the air in ways which probably would outdo some Olympic high-jumpers and aim her chakram in almost reality-defying ways (you know how she makes it fly off 5 different walls, precisely hit numerous bad guys and still is able to catch it), seem to hint as pretty much superhuman powers.
It does seem likely Xena has some divine blood in her but given at different points in the show Ares may have had good reason to tell Xena the truth but never did, I'd suggest it wasn't him. Further, I'd suggest it was just probably just some half-God (there have to be plenty considering the fondness of Zeus in particular for human women). In terms of what that means in terms of power level, it's unclear. Hercules was half human but could take on full Gods in a fair fight and win. I've read it suggested that this is because he inherited his physical abilities from his father (a very powerful God) which meant he could match or beat other Gods on a physical level, just not on a mystical level. So it's theoretically possible that even if someone were only a quarter-God, they would still have comparable physical abilities to their half-God parent who has comparable physical abilities to a full-God so Xena would be able to take on Ares.
The reasons I favour a half-God over a full-God are two-fold. First, in raw physical terms Xena doesn't have the same abilities as Hercules. Second, there are a lot of Xena lookalikes in the world.
There's Princess Diana, Meg, Priestess Leah, Lyla (a Hercules character), Lysia (from Hercules and the Amazon Women), Melinda (1940s) and Annie (1990s). Of all of these, Melinda maybe could be justified as having a resemblance.
So I would posit that there's a half-God character wandering around the Xena-verse, living for centuries, impregnating women throughout time. Hence all these Xena look-alikes are in fact half-sisters, explaining the resemblance (there may be a lot of other women who are also Xena's half-sister but we only notice the ones with a striking resemblance). Since their father isn't a full-God, many of the lookalikes simply didn't inherit any trace of the powers (or didn't tap into them, as Xena quite possibly didn't until dedicated herself to becoming a warrior).