The Crimson Storm is a revived alliance between the Forsaken and the Sin'dorei forces that re-took Silvermoon from the Scourge and has been re-taking Quel'thalas from Dar'khan's control steadely ever since. Their enemies lie partially in Alliance aligned humans from Stormwind aswell as the Kaldorei, both of which would gladly see the downfall of the Forsaken and the Sin'dorei. The main enemies of the Crimson Storm are the Scourge - With some Sin'dorei harnessing special hatered towards the San'layn, and some (most) of the Forsaken harbouring great hatered towards Arthas Menethil.