"Atavism…" With his thoughts confirmed by Sellifer's words once more, Valyr flashed a faint smile as he began to rummage through his treasure trove of memories regarding the concept.
In simple terms, atavism was the act of returning to one's origin. It was an act of retracing the path one's ancestors had taken in order to obtain greater power.
However, even though successfully achieving atavism would grant one access to power that would be impossible for one to originally wield, only a small number of beings would be able to achieve atavism.
For most, one would only either fail in their attempt at atavism, or only become partially successful in atavism.
And in most cases, becoming partially successful in atavism meant that their power would reduce rather than increase thanks to the deviations in the paths that they've retraced.
Then again, it's not like atavism was a nigh-impossible endeavor.