Clawstorm, Farie witch, Glowing Blob, Landmass, Banehunter. They all appear up to 2 area's before boss save for Clawstorm, which appears in the jails.
Farie witch appears in the Canyon of the Magi only.
So, Glowing blob is Act 3, Travinicial onward.
Land mass, is Act 4 City onward.
Bane hunter is Worldstone level 1 onward.
None appear on Boss area's.