Extended Survivor (20): Last for 45 mins in a Expansion Survival Map
Hell Raider (20): Conquer the Mellow Hills Abyss
Infernal Lord (20): Conquer the Golden Halls Abyss
Legendary Overlord (50): Defeat the 7th Hero in Legendary Mode
Lord of the Abyss (30): Conquer the Ruborian Desert Abyss
Soulblighter (20): Conquer the Evernight Forest Abyss
Guard duty
Always have blue minions on guard duty by holding RB and pressing X, Y. While on a guard post, they will actively run into the combat, grab a fallen peer, and drag their half conscious form over to you so they can revive their fallen comrade. However, while not assigned, they will wait for you to micromanage them over to the body by sweeping, making them almost useless in a large battle.
Water
When there is water in front of you or blocking your path, only you can walk through it. If your goblin minions go out of the shallow end of the water they will drown, and can only be saved by blue goblins. Instead of guiding your goblin minions across a complex path to keep out of the water (which they usually fall in anyway and drown), simply walk through the water. Your minions are smart enough not to follow you and will automatically seek the easiest path to get back to you. As long as you leave the Right Analog-stick untouched, they will not enter the water. Be careful; sometimes your minions cannot get through because a bridge needs to be activated (for example, Blue Goblin Cave).
Easy Max Imbued Gear
Forge a piece of gear without imbuing anything into it, then, go to upgrade it, put as many minions into it as you want and as soon as the animation starts but before any minions jump into the smelter, hit start to pause the game and exit, when you come back, the minions will have been imbued, but won't have been taken from your supply. Makes it real easy to get the Ultimate gear achievements...
First Troll
On Legendary, the first troll is very hard and consumes alot of minions. There's an easy way to completely skip him (Make sure you have 10 minions):
Head straight to the troll, and you'll get the cutscene of him getting ready to face you. After that, send all of your minions to open the gate where the crane is, and rush there (the troll will probably kill a few of your minions as they open the gate, but that's better than wasting 20 - 40 minions trying to kill him and also, if the troll is blocking the path, simple lead him away and head through the gate).
Once done, go to the crane and an autosave will occur. This is where the trick comes in: That autosave assumes you defeated the troll as you went further than you were suppose to, therefore, simply leave the area and come back, you'll find the troll has vanished as the game thinks he has been defeated.