Mission/Location related achievements

[Epic Fail X]

Thrombus and Keeping it real: Finish the main story.
Stark Raving mad: See following post!
Yes I bet you have: The Wretched Hive quest can be started in Frisktorp.
Wind Breaker: Roger and his pet can be found and killed in the medium co-op mission.
We are the freaks and I am so electrified: Cortex and ElectroBert can be found and killed in the hard co-op mission.
I scratched the surface: Limbo can be found next to Solside City. Descending to level 45 is everything but an easy task. Be sure to bring a lot of patience and money with you! The threat levels as follows:
10 - Limbo, level 1-8
11 - Limbo, level 9-20
12 - Limbo, level 21-28
13 - Limbo, level 29-36
14 - Limbo, level 37-40
15 - Limbo, level 41-?

[Nihilum]

If you go to Trollberga and talk to the guy who wants to start a party, he will hint you where his friend is, talk to him and you start a quest that ends with stark raving mad.

[OGZ]

How can one finish Stark Raving Mad? I finished the last quest (talked to the last guy in Dreamfield) but nothing happened. Maybe I did something wrong before but don't know what.

[Epic Fail X]

You can only enter Dreamfield after you completed the four required fetch missions. As you already are in Dreamfield you should have done everything correctly. Sounds like you ran into a bugged achievement to me. :(

[OGZ]

I was able to enter Dreamfield before the last fetch mission but when I left, it was locked until I finished last fetch mission. I tried to enter there because I was looking for the swamp and maybe things went wrong because it let me enter no matter lock icon was there...
Yea, it must be game bug that caused this because other players were able to get this achievement.

[Rage]

I just did same way like Ogisha said. And i have not got my "Stark Raving Mad" achievement :(