Originally posted by albert2wesker
you have to play the campaign to unlock the other stages and if you want to unlock the abyss mode on raid you have to complite the campaign on infernal
Not true.
You can complete the campaign on casual and it will unlock the first 20 levels on raid mode which are set to Chasm difficulty. In order to unlock Trench and Abyss levels, you just have to beat all the casual levels.
When you complete the 20th level on chasm, the first level of trench will unlock... so on so forth.