Suggestions, ultimately any changes are left to the discretion of the authors, but I study English and prefer things to make sense so can't really hold myself back.
Option #1:
REVENANKH inhabits tombs or crypts, avoiding light and training itself in peace. However, if anyone disturbs it, REVENANKH will chase the intruders for anything from a week to decades. - Helios
The verb 'inhabits' is not typically paired with the preposition 'to', on rare occasions it might be but this doesn't strike me as one of them. Generally 'inhabit' doesn't take a preposition. The 'has been known to' parts aren't very necessary, but occasionally a Pokedex entry will include this sort of thing, so if you want to keep it go ahead. I'd only us 'has been known' once though. I left 'tombs or crypts', although they are synonyms so I'd suggest choosing only one, other it's a bit like writing 'tombs or tombs'.
Option #2:
According to folklore, Revenankh are the mummified spirits of a deceased Pharoah's guard-Pokemon. They will hunt down any threat to their trainer, or his possessions. - Magmortified
You've put a full-stop in the middle of one sentence. I split the entry into two sentences. I corrected 'they are' to 'their' and also 'possessions'. I wasn't to certain about using 'It is said that...', it makes the whole first sentence passive - be bold.
Option #8:
Known in legends as the deathbringer, wherever REVENANKH goes all vegetation rots away. An aura of fear always precedes its appearance. - Rhykune
This is good enough. It does have an unnecessary comma so I removed it.
Option #9:
"It is said that REVENANKH have to train regularly to keep their physical form. Should one ever slack off, it will be reduced to mere bandages. - King of Anime
This is fine, I voted for it. Again, it suffers from passive contruction, ('It is said...' again), but so does half of the actual Pokedex in-game.
Option #10:
Though normally solitary, REVENANKH gather on full moon nights in remote desert locations. Contests of strength often follow. - King of Anime
Fine. The second sentence isn't a true sentence, you probably want to swap the period for a hyphen or a comma.
I hope people don't think I'm rude posting this, I don't mean it as a personal attack. I'm just a pedant.
EDIT: Nevermind. It looks like the one with no issues won anyhow. Good picking folks.