The Trial Grounds is a room used by the Ing to conduct rites of passage in Dark Agon Wastes. These rites of passage consisted of prearranged gladiatorial battles between young Ing and fierce opponents. A Luminoth corpse that Samus discovers here is apparently the remains of one such opponent.
- "According to Luminoth records, the Ing use this area to conduct rites of passage." —Scan Data (Metroid Prime 2: Echoes)
- "Young Ing battle fierce opponents to prove their mettle in combat." —Scan Data (Metroid Prime 2: Echoes)
- "It appears this Luminoth was one of their many opponents." —Scan Data (Metroid Prime 2: Echoes)
- "Nightbarbs are small airborne darklings. Smaller and weaker than a Hunter Ing, a Nightbarb will travel with a large pack to increase its odds of survival. This is wise, since their primary predators are Hunter Ing." —Logbook Data (Metroid Prime 2: Echoes)