The giant lizard creature is a large lizard-like creature with enormous teeth and claws. The creature has an extreme sensitivity to light which is why there's a need for tinted glass shielding on the lamps in its cell. Behavior varies among the species. The resident creature in the Old City Sanctuary's SHU is extremely vicious, while the female named Suki at the Tokyo Sanctuary is normally docile.
Episode 1x02 - "Sanctuary for All, Part II":John Druitt kidnaps Ashley Magnus and imprisons her in the creature's cell in an attempt to force Helen Magnus into giving him a vial of her blood which he needed to prolong his life. While Magnus is up in her study with John, she uses her computer to lower the screens in the main lab to relay a 'message' to Bigfoot, Henry Foss, and Will Zimmerman that Ashley is in mortal danger. Ashley tries to run up the enclosure wall and kick off a protective light filter, but the creature takes a swipe at her, knocking her down, then swipes again, slashing her throat.
As Magnus deals with Druitt, the three men make their way to the creature's enclosure and as Will and Bigfoot enter, Will sends Henry to go get Magnus. While Bigfoot tries and fails to control the creature with a hands-on approach, getting injured in the process, Will is able to use a loose pipe to knock off the tinted glass covering for the light Ashley had previously kicked, forcing the creature to retreat into the back of the cell long enough for Magnus and Henry to arrive to evacuate the three of them from the cell before the creature potentially killed them.
Episode 2x12 - "Kali, Part I":Suki is a female giant lizard creature who was affected by the wave send out by Big Bertha. Normally docile she escaped into Tokyo, Japan and ran amok in the city, no one was hurt but there was much panic. She was sedated offshore and the Tokyo Sanctuary built a new enclosure for her on one of their islands. The story was covered up by saying it was part of a big Hollywood blockbuster shooting at the harbor.
Trivia: This creature is assumed to be the same abnormal that had killed Mary Anne Zimmerman at an unnamed camp ground in 1985, mentally afflicting Will Zimmerman (who was eight-years-old at the time) for the rest of his life; putting him on a path to try to understand the world around him.
Trivia: There is no official name for this creature or its species. It is referenced as being a "lizard creature" and a "giant iguana" by Ashley Magnus.[1]