Big thanks to Gilthresa for putting these together, and allowing me along for the ride!
Umbrage for Umbriss
This achievement requires you to kill General Umbriss while he is affected with Modgud’s Malice. This buff to him is obtained when you kill a Malignant Trogg when it is near him. An easy way to obtain this achievement is to have someone CC the Trogg as soon as it spawns, keep CC on the add – DPS the boss to about 500k and then taunt the add over and kill it, then burn the boss.
Don’t Need to Break Eggs to Make an Omelette
For this achievement you have to not let the two adds that spawn after Shadow Gale cast Twilight Corruption at all, to achieve this you will need to split your DPS up on the two adds and put as many snares on that adds as you can – if you have a 70% movement speed reduction you will be able to get this easy.