"There's something different! You can't quite put your trigger finger on it. Your old pals are looking rather peaked, maybe even sickly. What the heck possessed them to climb into those coffins? Hmmm. Ah, well. Nothing a bit of supplementary lead won't cure... lead to the head, and put 'em to bed. Night-night, fellow Chosen. Poisonous dreams."
--C4L2: Battle of the Chosen loading text
ANCIENT ONE: INSECT, WE ARE THE ANCIENT ONE. BOW DOWN BEFORE US.
ANCIENT ONE: YOU ARE ALL THAT STANDS BETWEEN US AND THE DOMINION? PATHETIC.
CALEB: Oh, you're gonna hurt my feelings.
ANCIENT ONE: ALL THAT IS WILL NO LONGER BE. ALL THAT WAS HAS NEVER BEEN. ALL THAT WAS TO COME... UH, UM, UH...
ANCIENT ONE: ALL THAT WAS TO COME WILL NEVER HAPPEN.
CALEB: Enough talk, let's fight.
Caleb then has to fight each one, starting with Ishmael, then Ophelia, then Gabriella. They behave similarly to Caleb, and each has two weapons which they can switch between. Ophelia has a Tesla Cannon and Sniper Rifle. Gabriella has a Vulcan Cannon and Napalm Launcher. Ishmael has The Orb and, instead of a second weapon, exhibits magic similar to a Zealot, including the ability to teleport and heal. After defeating them, a hole in the middle of the arena opens up, clearing the way to The Ancient One .
There are various power-ups around the arena. The Chosen do not have any particular weakness, except to avoid their weapons. Fighting them is similar to a BloodBath (albeit with slower enemies)
It is unclear how they come about as they are can not be the original corpses of the Chosen from the original Blood as Ishmael was engulfed in fire by Cerberus and Caleb cremated Ophelia. It is unknown what happened to Gabriel's body but the undead form was female like his/her resurrected form Gabriella. It is possible that they were brought through the same sort of dimensional anomaly that lead to CabalCo accidentally resurrecting the Chosen with the Singularity Generator or that they were just affectations of the Ancient One and the The Nightmare respectively.