Heroes of the 2nd spawns just off the bridge, around x21, y17. There is an NPC you need to talk to, to initiate the FATE. I think the NPCs don't show up on the minimap if you're not close to them, when it spawned for me I camped over the bridge waiting for the NPC to rock up, then started the FATE.

I also waited an hour for the spawn, but maybe this info can help some people.