Only champions, and unique monsters, can draw the attention of heralds when killed.
And after you got the 1st message, you just need to travel in the area until you get the 2nd message and the herald pops close to you, no need to actually kill anything.
Basically, when monsters are generated in the area, a check is performed to see if the herald will pop there.
That means when you've "revealed" the whole map, the herald failed to pop there, you'll need to continue in another TZ area in that game.
This post was edited by xhul on Apr 7 2026 10:25pm