The Frozen Leviathan is the body of a deceased leviathan class creature located within a large wall of ice at the Phi Excavation Site.

The body was first discovered by Fred Lachance, who would report back to Alterra about his findings. Following its discovery, corridors were cut into the ice around the creature, and various walkways were erected to better study the creature and its infection.

The Frozen Leviathan is a heavily-built creature with a broad body, four limbs and a long tail. This species is one of the largest seen to have lived on 4546B, much like many of the other extinct Leviathans found throughout 4546B.

Running from just behind the shoulders to near the end of the tail is a row of large overlapping plates which gradually decrease in size as they move towards the tail. The tail is flattened laterally, and longer than the entire body. It is slightly broadened at the tip to assist with propulsion.

Its four limbs are heavily muscled and each ends with a five-digited paw. Each digit is tipped with a large claw. Additionally, on the undersides of each forelimb are three plates resembling those seen on the back. There is a small amount of webbing between the digits.

The head is broad, relatively flat and has a wide mouth filled with thin, long teeth; 34 in the lower jaw and 40 in the upper, for a total of 74. Placed behind the mouth on each side is a large sickle-shaped bony plate which projects straight forwards from the head. Another structure which is similar to these plates but smaller and pointing backwards rather than forwards is found further back on the head. The eyes are side-mounted and deeply recessed into the head.

The creature is noticeably infected with Kharaa.

Parvan's log suggests that Fred thinks the leviathan is still alive, though Parvan expresses his disbelief in his security report. It has been confirmed several times by developers to be dead, however.