Makai Senki Disgaea 2/Dark Sun World

Dark Sun World

Initial opening Requirement

First you must find and activate switches hidden around the town.
After you find the required amount, (2~5) A Black Archer will appear in the corner closest to what appears to be the town entrance.
After speaking with her 3 times she will challenge you to a fight.
She is lvl 100 so she shouldnt be too hard for a group of 40s or so.
Once she is defeated She will act like a normal gatekeeper transporting you to stages.
You'll only have access to 1-1 at first even if you met requirements to unlock the stages before the stage isnt unlocked untill Black Sun is unlocked.

Some Dark Sun World stages will automatically draw you in once you fufill the requirement. However, most of these stages will not do this if you are playing through the stage for the first time (and the stage can be opened the first time playing through).

Requirements:

1-1 Given from the start.
1-2 Defeat 2+ enemies with one move.
1-3 Take damage from an enemy. (You will get drawn into the Dark Sun World once this is completed.)
1-4 Kill a green mage - there's one on the panel where Axel used to be at, but killing one of your own counts too. (You will get drawn into the Dark Sun World once this is completed.)

2-1 Clear within 2 turns. Make sure you destroy the geo panel as well.
2-2 Clear within 1 turn. Free Stage Only
2-3 Clear stage without moving more than 3 times total.
2-4 Pick up an enemy or one of your own characters. (You will get drawn into the Dark Sun World once this is completed.)

3-1 Let 11 turns pass. (You will get drawn into the Dark Sun World once this is completed.)
3-2 Destroy a geo symbol. (You will get drawn into the Dark Sun World once this is completed.)
3-3 Make a 5 person tower. (You will get drawn into the Dark Sun World once this is completed.)
3-4 Clear without lifting anything.

4-1 Destroy the red geo panels using the transparent symbol. (You will get drawn into the Dark Sun World once this is completed.)
4-2 Merge 4 enemies into another one.
4-3 Merge all the enemies together. (You will get drawn into the Dark Sun World once this is completed.)
4-4 Let 30 turns pass. (You will get drawn into the Dark Sun World once this is completed.)

5-1 Let one of your party members die. (You will get drawn into the Dark Sun World once this is completed.)
5-2 Clear the stage using only one character. Free Stage Only.
5-3 Make an 8 person tower. (You will get drawn into the Dark Sun World once this is completed.)
5-4 Clear without using regular, counter, or special attacks. Only tower attacks and throwing onto the base panel allowed.

First half of the colliseum

6-1 Make a 10 person tower. (You will get drawn into the Dark Sun World once this is completed.)
6-2 Defeat all enemies after destroying the geopanels. Free Stage Only.
6-3 Merge 5 enemies into another one.
6-4 Blow up all of the Prinnies at once.

Second half of the colliseum

7-1 Destroy all Geo Panels. (You will get drawn into the Dark Sun World once this is completed.)
7-2 Clear stage without taking any damage.
7-3 Throw an enemy into one that is being held by one of your characters. (You will get drawn into the Dark Sun World once this is completed.)

8-1 Destroy the geo symbol so that it forms a chain. (You will get drawn into the Dark Sun World once this is completed, even on your first time through.)
8-2 Destroy the moving "No Entry" geo symbol. (You will get drawn into the Dark Sun World once this is completed, even on your first time through.)
8-3 Defeat all enemies using only regular attacks.
8-4 Clear stage without taking any damage.
8-5 Get your bonus gauge above 4.
8-6 Throw an enemy into one that is being held by one of your characters. (You will get drawn into the Dark Sun World once this is completed.)

9-1 Move to the highest spot on the map. It's towards the back, 64dm. (You will get drawn into the Dark Sun World once this is completed.)
9-2 Clear within two turns?
9-3 Get your bonus gauge above 2.
9-4 Move onto the head of the center serpent (84dm). (You will get drawn into the Dark Sun World once this is completed.)

10-1 Merge 4 enemies into another one.
10-2 Destroy the geo panels. (You will get drawn into the Dark Sun World once this is completed.)
10-3 Get the TOTAL DAMAGE value over 1000. (You will get drawn into the Dark Sun World once this is completed.)
10-4 Get your bonus gauge above 3. (You will get drawn into the Dark Sun World once this is completed.)

11-1 Clear without taking any damage.
11-2 Destroy the geo panels except for the yellow one.
11-3 Get the TOTAL DAMAGE value over a certain amount, possibly 1000. (You will get drawn into the Dark Sun World once this is completed.)
11-4 Clear stage with one character?
11-5 Clear using just regular attacks.
11-6 Clear without taking damage.
11-7 Clear without using regular, counter, or special attacks. Only tower attacks and throwing onto the base panel allowed.

12-1 Merge all the enemies together. (You will get drawn into the Dark Sun World once this is completed.)
12-2 Clear within 2 turns.
12-3 Make a 9 person tower. (You will get drawn into the Dark Sun World once this is completed.)
12-4 Make a 3 person tower. (You will get drawn into the Dark Sun World once this is completed.)
12-5 Clear with one character.
12-6 Get the TOTAL DAMAGE value over a certain amount. (You will get drawn into the Dark Sun World once this is completed.)

13-1 Clear without taking damage.
13-2 Get the TOTAL DAMAGE value over a certain amount, possibly 10,000. (You will get drawn into the Dark Sun World once this is completed.)
13-3 Destroy all geo panels. (You will get drawn into the Dark Sun World once this is completed.)
13-4 Get the TOTAL DAMAGE value over a certain amount. (You will get drawn into the Dark Sun World once this is completed.)

Confirmed that 2-1 Requires the Geo Symbol to be destroyed as well
Total Damage Value refers to the damage a Combo does so remember to use a AOE effect to make it span over multiple enemies.
Free Stage means you can only open a B.S. Stage after clearing the stage as a story stage (such as, go to stage 2-2 after the story and do the requirements listed to open 2-2 of the dark sun world)
Thanks go out to Futantshadow for posting the rest of the B.S.W. requirements. Akuma Hokoru