Master Rufus's office (formerly)
It was previously imprisoned in a small cage in Master Rufus's office until it managed to blackmail Rufus's apprentice, Callum Hunt, into letting it go after it caught him sneaking around the office. It was then that Call gave Warren his name, which Warren gleefully accepted, interpreting the word as the underground dwelling of creatures.
For a while, it slept in Call's room. During a task Call and his friends endeavored that eventually got them lost and wandering the Magisterium tunnels, Warren was sent by another fire elemental, the Devoured Marcus, to lure the children back to his cavern. Warren returned to the children and falsely offered to help them get back to Rufus; the children agreed, and Warren led them straight to the Devoured, much to Call's disappointment.
Warren once again revealed himself to Call while the latter was relaxing at one of the underground lakes in the Magisterium, telling him that he lived there and watched him.
Eventually, Warren was recaptured by Master Rufus. As part of Aaron's training, he ordered him to make the lizard disappear into the void with his chaos magic. Also unwilling to bring the lizard into the void, Aaron was easily convinced by Call to simply "disappear" the whole cage, allowing Warren to escape through the smoke while the cage disappeared.
Later, he once again showed himself to Call, giving him an ominous warning: "The end is closer than you think."
Warren is a small lizard with blue flames and curved spines running along its back. It has luminous, bright gold eyes, distinctive of its fire elemental nature.