"Then Fëanor swore a terrible oath. His seven sons leapt straightway to his side and took the selfsame vow together, and red as blood shone their drawn swords in the glare of the torches. They swore an oath which none shall break, and none should take, by the name even of Ilúvatar, calling the Everlasting Dark upon them if they kept it not; and Manwë they named in witness, and Varda, and the hallowed mountain of Taniquetil, vowing to pursue with vengeance and hatred to the ends of the World Vala, Demon, Elf or Man as yet unborn, or any creature, great or small, good or evil, that time should bring forth unto the end of days, whoso should hold or take or keep a Silmaril from their possession.
Thus spoke Maedhros and Maglor and Celegorm, Curufin and Caranthir, Amrod and Amras, princes of the Noldor; and many quailed to hear the dread words. For so sworn, good or evil, an oath may not be broken, and it shall pursue oathkeeper and oathbreaker to the world's end."
J. R. R. Tolkien, The Silmarillion, Ch. 9: Of the Flight of the Noldor
Print available here! [link]left to right: Amrod and Amras (they're hard to tell apart in this light), Fëanor, Curufin (always the first to obey his father), Maglor (not really conviced but caught up in the moment), Maedhros (taking charge of keeping his brothers in line while Atar is busy), Caranthir, Celegorm.
Watercolour and gouache.
early stages [link]
(Including a 1995 version of this... with Maedhros in mint-green tights)
painting steps [link]