5. I selected the No Hell Terrain option, but while exploring, around turn 200 I ran into a bunch of it. Some even had Penguins on it. I think the culprit might be the Archos who also seem to have gotten lucky with a Lich although I didn't know one could create hell terrain. At any rate, no use in having that option for no hell terrain if it can be overridden.
The No Hell Terrain option, might be better named No Hell Terrain Spread. That is any hell terrain created in the world builder, or through spells, exploration, etcetera remains hell, it just doesn't spread.
(Infernal territory becomes hell as part of the spread.)