Some errors:
First paragraph:
is as(a) legendary Ground-type Pokemon
is(in) a beacon of Harsh Sunlight.
because once this creature start(starts) to regain
Third paragraph:
It’s(its) control over the land is so great
but it is a among the most powerful of Ground-type attacks
(There is an extra a)
Fourth paragraph:
its Drought Ability is upgrade(upgraded) to the cataclysmic Desolate Land Ability
bringer of a drowned apocalypse
(This bit just feels somewhat off to me. Not really an error.)
Fifth paragraph:
managed to eventually awaken the might(mighty) beast with
(I also recommend specifying how 'recent' such events are. While 10 years is technically recent, it simply exacerbates the thinking that the Magma/Aqua incident occured as recently as a few months ago in-universe.)
Last paragraph:
unrivaled in on and within the land.
(in is not necessary)
All good.