Story related and cannot be missed.
Enter the Invulnerability Hunter, the final of the three Hunter bosses. This one is easily the hardest of the three, possibly even the hardest boss in all of Doom 3.
What you’re going to want to do is right when the battle begins, jump away to the right or left and avoid his attacks. Keep moving during this fight to avoid as much damage as you can.
You will have noticed that a power core failed, resulting him to be vulnerable to attacks. While there is a static-like effect over his body is when he is vulnerable. Simply use the Bloodstone and let him have it while he can be hurt. When you see him beginning to power back up and the static effects get stronger, you will need to open the power core covers by pressing the control panels on them when they are green and then destroy them.
Repeat this process to take him down. Just watch out for his melee attack as it does massive damage.