In this video guide I will show you how to defeat Mammon one of the Lords of Hell. This fight is not too bad, just make sure your power level is as high as the recommended level. So depending on your fighting style it might be different than mine. I personally prefer to use Strife and keep my distance. Then use War when his health gets low. Also make use to use War's block ability for this fight. It will help out a lot. And having the health upgrade for whoever is swapped out regains health, upgraded as high as you can .
As far as Mammon's moves go. They are pretty basic at first. He will disappear, melee you, and shot you. Later on he will use artifacts to do different things to you, like summon minions or summon a hammer to smash you. Just make sure you take them out first. Or you may have a harder time defeating him. By the time you take out an artifact, then continue to attack him for a bit he will spawn another one. Just keep doing the same method until he is done spawning artifacts. When he is almost dead he will have one move you need to watch out for. That is his beam he shoots out. It's very powerful and has some distance to it. You could negate some of the damage with War's block. Or safest bet is to try and get behind him then attack him. Just keep on him until he is dead. The achievement will pop at the end of the cut scene.