Rangers are the might heroes of Rampart.
"Rangers are warriors born of the woods, skilled at hunting and tracking. Their dedication to the protection of the wilderness leads them to pursue a wide range of knowledge, concentrating on martial and outdoor skills." RoE manual
As they are heroes of a good town, this allows them to get experience on Altar of Sacrifice and in Grotto for artifacts only.
Rangers cannot learn Necromancy and Fire Magic, which means they can only acquire them from Witch Huts (if allowed), Scholars, Seer's Huts, Pandora's Boxes or Events.
In Horn of the Abyss, Thorgrim is banned by default, because his specialty is Resistance. This secondary skill is also banned by default, being replaced with Interference, therefore, Thorgrim is replaced by Giselle, whose specialty is Interference.