Isabella (Known as Catleia in the European version of the game) is a CO of the 12th Battalion. She is a young girl, with white hair and pale skin, rescued from a building by Will. She has no memory of who she is, though somehow knows detailed military information. Eventually she grows an attraction to Will which throughout the game becomes more and more apparent.
She first appears in Stage 2, "A Single Life". She is barely alive, but manages to hold on long enough to get back to camp. There, the heroes (Lin, Brenner, and Will) learn that she is amnesiac, but knows detailed knowledge about the Rubinelle Military. Brenner attempts to give them a safe refuge at a town called Freehaven, but after a few skirmishes with a pack of raiders led by The Beast, Will and the other civilians with Brenner decide to stay with him and the battalion.
Isabella got her name when Will finds a plastic flower in some ruins and gives it to her. She remembers what the flower is called; Callyetta Isabella. (In the European release the flower is simply called a catleia). She takes her name from this Will then dubs her Isabella because Callyetta is too hard to pronounce.
After Caulder preforms his "Fear Experiment", the heroes learn about the virus the Creeping Derengea, or "The Creeper". Isabella becomes infected with the virus, since it only affects young people for some reason. Will is frightened and runs from her since he doesn't want to become infected, but is later ashamed of this act and apologizes. The heroes manage to get to a nuclear shelter constructed for Rubinelle's political elite in case of and all-out nuclear war with Lazuria. Interestingly enough, Isabella was the one who told them of its existence. Also, ever since she became infected with The Creeper, she was randomly muttering a ten-digit number; the password needed to get into the shelter.
Eventually, the heroes learn who she is: one of the cloned children of Dr. Caulder. This causes the civilian opinion to turn against her. Deeply hurt, she leaves camp and surrenders to Caulder. She is placed in the laboratory on board the Great Owl.
Will decides to rescue her, reinforcing the idea that he is experiencing some sort of attraction to her. As he puts it: "I couldn't care if you came from a mother or a tank!"
When the 12th pursues Caulder to the Nest, she gives the 12th the information needed to destroy the Nest (smash the laser cannons). She has apparently comes to terms with her origins, and wishes to prove that one's origins do not dictate how they turn out.
After Caulder's death, the twosome live together happily ever after.
CO powers
Normal CO power - Deep Strike/Overlord
+2 Movement to all Units, +2 Range to all Indirect Combat Units.
| 12th Battalion | |
| COs: |  Brenner |  Isabella |  Lin |  Will
|
| IDS | |
| COs: |  Caulder |  Penny |  Tabitha | Cyrus
|
| Former COs: | Isabella
|