race features:
Darkvision. Thanks to your infernal heritage, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in darkness, only shades of gray.
Frozen Resistance. You have resistance to cold damage.
Icy Legacy. You can cast the ray of frost spell with this trait. Starting at 3rd level, you can cast the armor of Agathys spell with this trait. Starting at 5th level, you can also cast the hellish rebuke spell with it, dealing cold damage in place of fire damage. Once you cast armor of Agathys or hellish rebuke with this trait, you can't cast that spell with it again until you finish a long rest. You can also cast these spells using any spell slots you have of the appropriate level.
Intelligence, Wisdom, or Charisma is your spellcasting ability for these spells when you cast them with this trait (choose when you select this race).
While most
tieflings resist fire, those whose ancestry can be traced back to
Stygia, the frozen fifth layer of the
Nine Hells, will sometimes find their power based in cold rather than flame. These are individuals with the blood of
ice devils flowing through their veins, or even that of the archdevil
Levistus himself. The skin of these tieflings is bluish-white like ice or blackish-purple like frostbite, and their horns are always crystalline, as if they were sculpted from ice.