Professor Van Horn is a unique encounter, it will randomly respawn after it is killed.
Professor Van Horn
Newland Desert - 2865x1580
Located in Newland Desert (2865,1580)
Faction : Monster
It is located NE of NLD whompha, in Rhino village. Exact spawn place is usually indicated by various camp. It's one of mobs with high health regen and high damage. Among the various high level unique encounters, Prof. Van Horn has a significantly high heal delta for his level. Do not be surprised by how difficult it is to kill him.
Both items drop in various qualities. Drop rates aren't consistent, which means that you can still walk away empty handed. Interesting thing is that while this mob is called Professor Van Horn, it seems to be wearing someone else's vest.