Damage Resistance
In most D20 games, Damage Resistance factors in the existence of magic weapons and commonplace Spellcasting, things that are far from common in Hyborea. To compensate, listed Damage Resistance should be divided by 5. If the creature is wearing armor, use that armor’s AC bonus as its DR. Add in Natural Armor bonuses as well.
(DR ÷ 5) + Armor
For example, an OGL creature is listed as have DR 40 and Natural Armor of 7. This would be a DR of 15 in Conan (DR 40 ÷ 5 = 8, +7 = 15).
Many creatures have conditions listed with the DR rating. Ignore anything with a “+” after the slash, such as DR 15/+1, indicating that a +1 or better weapon is required. Any conditions that can be met in the world of Hyborea can be retained, such as DR 20/silver (damage reduction is ineffective against silver weapons) or DR 15/bludgeoning (ignore Dr on damage done by bludgeoning weapons).