Imagine this if you will: Captain Rex, a few years older than we last saw him in the Clone Wars. Sometime shortly after the mess of order 66 and whenever he had his chip removed- curled up sleeping on a ratty bed on some backwater planet. He's alone at this point, Ahsoka has gone into hiding, and he's separated from his brothers. He's having nightmares. He twitches in his sleep; his fingers moving, and his face twisting into expressions of pain and terror. He sees, in his mind's eye, himself standing, armored, and surrounded by thick, red and gray fog and dim reddish light, and out of that fog, all around him, echoing; he hears it- A deep, mocking laughter, and a voice: "You should have listened to the ARC trooper from the beginning Captain! ...He was right! I was using you…."
"Rex!" he can suddenly hear Fives screaming in warning. "REX!" his dead brother's voice echoes from all sides. Finally, he spots Fives, in a distant pocket cleared of the fog. Rex calls out and reaches for him, just as Fives screams again. Suddenly the hooded figure of Palpatine appears behind the ARC; and before Rex can even choke out a warning, he runs Fives through with a blood red blade. The sight of the fiery weapon jutting from Fives chest is too much to bear. The hooded figure looks right at him, yellow eyes boring right into Rex's soul.
"You've all been my pawns…" the Sith rasps before lunging for the Captain.
Rex screams in horror as he jolts awake, sitting right up in bed and throwing the thin, tattered sheets off, despite his sweat causing them to cling. He pants heavily for a few minutes, struggling to regain his calm composure. He eventually closes his eyes and lays back down as tears flow freely down his face. "I'm sorry Fives…."