"Thanks for your help back there. And as for my wound? Don't worry about it. It'll take more than that to keep me down." - Cas to Rion.
Cas (キャス) is a soldier in Galerians: Ash that works under Major Romero. Cas encounters Rion for the first time when she and her soldiers are fighting near Hangar No. 3 against Parano's forces. She is surprised to see Rion is actually back from the dead but refuses to retreat, saying she obeys only her superiors and that she is ready to destroy the entire area if Parano would manage to kill Rion (who simply concedes to her.) After the boy wins the battle, she says she is glad for his help.
Cas is very skilled and has the respect of her comrades. Unlike most of the military personnel, she does not fear Rion and becomes a good friend of his. During the second assault, she is sent by Romero to protect the office on the first floor, but she is ordered to retreat after a short battle. After a tactical reunion, Major Romero orders her to take her men and for the enemy on third floor, and she reluctantly obeys. Cas is also the one who told him about the hacker-pilot Pat, who later uses his Air Beagle to transport Rion between the air base and Ash's uranium refinery. Before Rion leaves, she swears she will protect Lilia. When Rion comes back, she recognizes his voice behind the barricade door for the third floor, and opens it. She assures Lilia is safe; however she looks to be slightly jealous Rion didn't ask about her also. Rion is embarrassed, but Cas starts to chuckle, saying that after all, she is a soldier and it would be a bad sign if Rion was worrying about her. She does not seem to have a terribly good opinion of Romero but she still follows his orders regardless.
When the airbase armory is attacked by Ash's forces, she detonates a bomb, destroying the place and slowing down the invasion albeit sacrificing her life in the process. Rion, thanks to Lilia's telepathy, is able to sense it, started to feel something is wrong while he was trapped in Nitro's world. The player (upon returning to the real world) can go back to the armory and find Cas' corpse. If investigated, Rion will mourn for her death and the player will be rewarded for remembering Cas with a Recovery Plus, Breakaron, and Bustanor.
- Cas' name is similar to Casca, a character from Berserk. Both are woman soldiers with a high rank in their army and the respect of their subordinates, both grew affectionate in some way towards the protagonists of the stories where they appear, have a masculine personality but also a softer, still hidden side, and both are betrayed by their commander. Still Casca survives, in some way, while Cas dies.
- Cas shares some features with Vasquez, a character from the Alien 2 movie. Both are masculine female soldiers, both have the respect of their comrades and both die committing suicide with a grenade to slow down an invasion of monstrous enemies. However, Cas is shown to be much more rational, calculating, and cautious.
- The firearm Cas uses resembles the MP5 sub-machine gun. All the other soldiers in Galerians: Ash are seen wielding the same weapon except for Romero, who instead uses an assault rifle similar to the M16.