According to the lore text at the bottom of the card, the creatures are trapped on a rock (possibly an asteroid.) Someone left behind an encrypted log recording the existence of slivers, either an unlucky explorer or, perhaps, a scientist involved in experimenting with the creatures, which would be a nice callback to the Riptide Project
Every professional grading company assesses cards against the same four core criteria
7 Steel Overseer Artifact creatures don't have very many creatures with Lord effects, creatures that grant all creatures of a specific type a boost to their stats or abilities
Despite its bulk, it deftly feints every which way, leading opponents on a deceptively merry chase as it all but dances around them. Attacks Boulder Crush50 Scorching Horn80+ If this Pokmon has any Fire Energy attached, this attack does 80 more damage, and your opponent's Active Pokmon is now Burned