Thardus is a large, sentient stone creature composed entirely of Phazon Ore. It is a specimen of the Space Pirates' Project Titan, an animation experiment which consists of exposing inanimate objects to Phazon radiation in an attempt to bring them to life. They attempt to tame it and consider placing it on patrol in the Phazon Mines, but due to violent behavior, resulting in massive casualties, Project Titan is suspended indefinitely.
The chaotic nature of Phazon caused weaknesses in Thardus' structural integrity. At first, Samus is unable to target Thardus' weak points due to Phazon radiation given off, but by using her Thermal Visor, she is able to target the high concentrations of radioactivity given off by the Phazon Energy, which binds the stones of its body together, and weaknesses in the casing. When the target area has sustained enough damage, weaknesses become visible to her Combat Visor. After Samus destroys the weak points found on various parts of Thardus' body, it is no longer able to hold itself together and collapses.
Thardus attacks by throwing large rocks telekinetically, rolling directly into opponents, and by encasing objects in ice.
- If Samus has obtained the Plasma Beam or Power Bombs through Sequence Breaking before she fights Thardus, she may use them to inflict massive damage in a short amount of time.
- If Samus returns to the exact spot where Thardus was found, an adult Sheegoth (which itself was the main enemy in a boss battle) can be found resting there instead.
- "Quarantine specimen exhibits highly aggressive behavior. Its body structure, composed of Phazon ore, appears nearly invulnerable. This has rendered our efforts to train and discipline subject useless." —Scan Data (Metroid Prime)
- "Research on Tallon IV is expanding into new areas. Pending stabilization of the Thardus venture, we will expand Inanimation research to include other native Tallon IV materials." —Scan Data (Metroid Prime)
- "The taming of Thardus continues. Barring unforeseen setbacks, it can be installed on Phazon mine patrol by Lotus Milestone." —Scan Data (Metroid Prime)
- "Project Titan is suspended indefinitely. Security breaches resulting in massive casualties have occurred. Access is strictly prohibited until further notice." —Scan Data (Metroid Prime)
- "Project Titan specimen is immobilized in Quarantine Cave. Relocation is recommended due to increased violent activity." —Scan Data (Metroid Prime)
- "Phazon ore appears to bind through Phazon energy. Thermal Imaging is required to detect the highest concentration of radioactivity, which serves to bind the stones together." —Scan Data (Metroid Prime)
- "Although the armor-like qualities of this shell provide ample protection, Thermal Imaging can be used to detect weak areas in the casing." —Scan Data (Metroid Prime)
- "An animated, sentient creature of stone charged with Phazon radiation. The Phazon radiation given off by Thardus negates auto-targeting systems, preventing lock-on. It may be possible to acquire alternate targets with a different Visor. The chaotic nature of Phazon irradiation leads to instability in its structural integrity. Thardus can encase targets in ice, and its colossal size and strength make it a formidable opponent." — Logbook "Thardus" (Metroid Prime)