In New Game + the "Black enemy with Red Eyes" will drop new kind of upgrading material (Silver ORE). I collected around 20 in the whole run. With 3 of this you can make your first Armor Upgrade at Maker's Forge. Go to Ulthane and choose update armor. The upgrade costs 3 -> 6 -> 9. After 9 you will need new material of it (Fragment) for upgrade, but unfortunately I didn't get any on my first New Game+ (Armageddon). With the upgrade your Armor will get better stats. You can upgrade your basic armor, but you can get better Armors in Crucible DLC, if you have it. After the first New Game + you will get a new armor at start, which grants you better damage, more lurchers for killing, and more lurchers if shattering crystals.
If you are going for level 100 recommended to DO NOT SHATTER any crystal you collected in New Game +, so you can get at least 10% more of them (with the new armor) at the beginning of the NewGame+2, immediately after finished the previous game!