Gardon Ironhide, Warpriest of the Good Fiend (5e Creature)
From D&D Wiki
Large fiend (gardon), lawful good
Saving Throws Dex +9, Con +9
Magic Resistance. The Gardon legionary has advantage on saving throws against spells and other magical effects.
Magic Weapons. The Gardon legionary's weapon attacks are magical.
Innate Spellcasting. The Gardon Warpriest's spellcasting ability is Charisma (spell save DC 19). The pit fiend can innately cast the following spells, requiring no material components: At will: command, burning hands 1/day each: suggestion, mass healing word
Devil's Sight. Magical darkness doesn't impede the Gardon legionary's darkvision.
Multiattack. The gardon makes three melee attacks.
Mace. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) bludgeoning damage + 10 (3d6) fire damage
A pit fiend was summoned by an evil gnomish wizard to do his bidding but the spell went wrong and they switched forms the pit fiend tried to get his proper form back by studying magic after many years the pit fiend became an archmage and took his own form back bringing hes skill as a wizard into his new for but during his time as a gnome he grew to care for humanoids and slowly became good he used his power to create the gardon race.