Damaging the Empyrean Sentinel
To damage the Empyrean Sentinel shoot the particular face that is glowing blue:

Shoot the face of the Empyren Sentinel that is glowing blue, in the Beginning of the End in Borderlands: The Pre-Sequel.
Once you have taken out the shield shoot the area that is glowing either purple, blue or green.
It is a good idea to leave some of the adds alive so you can use them to get second wins in case you die. However, you need to keep moving around so you don’t take too much damage from them.
Attacks of the Empyrean Sentinel
The attacks of the Empyrean Sentinel you have to worry about are when the pillars come from the ground:

One of the Empyrean Sentinel’s Attacks where pillars rise from the ground in The Beginning of the End in Borderlands: The Pre-Sequel.
It means that you will take a lot of damage if you touch the ground so be sure to stand on the pillars. Whilst you are waiting for the attack to stop is a good time to kill the various adds that are flying around the place.
Another attack you need to be careful of is when the Empyrean slams down his arms and spits acid everywhere:

An attack of the Empyrean Sentinel where he spits acid everywhere in the Beginning of the End in Borderlands: The Pre-Sequel.
Be sure to get out of the area between his arms as soon as you realize what he is doing.
Another attack is a giant ball that pulls you towards it. You can get away from it a little by using your boost but I didn’t find that the attack did very much damage. Other attacks are column attacks that either come out of the ground or from the Empyrean Sentinel’s hands.
Whilst keeping all of that in mind keep shooting at the Empyrean Sentinel’s Faces until you have killed it.
Excellent, concise and helpful. Thanks!