16 cards where the name includes “fiend” and the colors is R

Bogardan Firefiend (Planechase #48)
Fiendish Duo (Murders at Karlov Manor Commander #153)
Fiendlash (Commander Masters #221)
Firefiend Elemental (Magic Origins #146)
Gibbering Fiend (Shadows over Innistrad #161)
Goblin Fire Fiend (Ravnica: City of Guilds #127)
Heckling Fiends (Conspiracy #145)
Henchfiend of Ukor (Time Spiral Remastered #170)
Hobblefiend (Core Set 2021 #152)
Kiln Fiend (Jumpstart #338)
Kuldotha Flamefiend (Double Masters #134)
Slag Fiend (New Phyrexia #95)
Spark Fiend (Unglued #51)
Tectonic Fiend (Time Spiral #181)
Tibalt, the Fiend-Blooded (Duel Decks: Sorin vs. Tibalt #41)
Torch Fiend (Jumpstart #367)

Though this query has ended, its relics still slumber in New Argive.