The giant lizard was a gigantic heroic reptile, and Teegra's lover, residing in the jungle surrounding Firekeep. It attacked Juliana's warband of sub-humans when they where searching for Princess Teegra in the deep jungle, killing several of them.
Attack on Julianna's warband
When searching for the escaped Teegra, the warband sent by Queen Julianna accidentally disturbed a giant lizard resting in the jungle. The lizard quickly killed the nearest sub-humans by stepping on them and then used it's massive tail whip another two aside. It then devoured one of the nearby corpses, before sauntering away.
Before that happened however, Teegra gained the lizard's attention, which it then fall in love with her, and only wanted to play with her, which she took off her microkini, showing the sign that not only does she accepts, but she also like lizards. So the two swam in water together, and then they played a game of Cat and Mouse, and whoever wins gets to have the other feel their belly. Even though Teegra was good at the game, the lizard was even better however. But when it won though, it instead gave Teegra a lick, which it shows she can trust it has kindness and responsibility within itself, and let her loose, because both of them wanted to save the world from Juliana, Necron, and their sub-human orc like ape horde. So she put her microkini back on herself, and then ran off into the woods.
It is actually not impossible that the giant lizard was still alive when Jarol released a lava flow to destroy Icepeak, as it first had to flood the jungle.