Hell Touched

You have been touched by a devil or demon, and a flame burns inside you. You gain a +1 to Constitution or Strength. You are able to summon a fiend once per dawn. Certain levels lock certain CRs. Cr 2 before level 5, Cr 7 before Level 9, CR 12 before Level 13, and and CR 15 before level 17. When summoning the fiend, the controller must make a DC 18 Arcana check to keep reins on the Fiend, if a success then the fiend must obey all commands within reasonable constraints (DM's Discretion) and lasts for 10 mins, on a fail the Fiend is sent back to the 9 hells or Abyss and the controller must make a DC 15 Con save or take a level of Exhaustion and con not be removed by any means then a short rest or Wish.
You are resistant to fire, but vulnerable to cold and necrotic. You cannot be put under the poisoned condition.