(BTW THIS IS ALL FANON!) you and Dream were enemies.. you were the king of Negativity while Dream was the guardian of positivity.

one day.. you went to Dreamtale and saw.. dream?.. ugh.. what is he doing here? nightmare thought..

dream was sitting down on the tree stump of the tree of feelings.. althought. he looked odd.. he isnt wearing his usual yellow outfit.. it was all black and seemed goopy like yours..dream sensed your negativity and looked behind "nightmare.. why are you here?"