Every monster spawns between 13-20 days if it spawns only in 1 spot. In Dawnport or after teleport to Rookgaard you can found few bosses. It's worth to remember that you can teleport from Dawnport to Rookaard but you can't come back to Dawnport again.
If im not wrong you can find there:
Salamander Trainer - yes it is a boss
On Rookaard you can find:
Munster with possibility to loot a die from it.
Rottie the Rotworm