The Ruins Test is a Varia Suit-clad Chozo warrior ghost faced by Samus Aran as a miniboss in Metroid: Zero Mission.
In a Chozodia temple, a suitless Samus Aran intercepts the ruins to find the ghost of a Chozo warrior, donned in ancient armor. After battling and defeating the phantom, Samus gains the legendary Varia Suit, a Plasma Beam to go along with it, and the various "unknown items" she collected that were incompatible with her Power Suit.
The Ruins Test served as inspiration for Dark Samus, the main antagonist of the Metroid Prime trilogy.
Metroid Prime 3: Corruption