Many of the Alliance and Horde have drowned and died into Nazjatar and soon Nya'lotha will surface as a vision of N'Zoth. More bodies will be claimed and it seems like Calia will be using the Light instead to ressurect more Forsaken many of which will be victims from Ogrimmar, Stormwind and Boralus.

Derek could be the allied race leader of a Kultiran equivalent for the Horde which are basically undead pirates/ drowned.