Existem algumas evidências de que as espadas élficas da Primeira Era brilham na presença de Orcs. Da Sociedade do Anel (ênfase minha):
After only a brief rest they started on their way again. All were eager to get the journey over as quickly as possible, and were willing, tired as they were, to go on marching still for several hours. Gandalf walked in front as before. In his left hand he held up his glimmering staff, the light of which just showed the ground before his feet; in his right he held his sword Glamdring. Behind him came Gimli, his eyes glinting in the dim light as he turned his head from side to side. Behind the dwarf walked Frodo, and he had drawn the short sword, Sting. No gleam came from the blades of Sting or of Glamdring; and that was some comfort, for being the work of Elvish smiths in the Elder Days these swords shone with a cold light, if any Orcs were near at hand. Behind Frodo went Sam, and after him Legolas, and the young hobbits, and Boromir. In the dark at the rear, grim and silent, walked Aragorn.
Fellowship of the Ring Book II Chapter 4: "A Journey in the Dark"
Há suporte limitado para isso em O Silmarillion . A espada de Túrin Turambar, Gurthang (anteriormente Anglachel), é descrita como brilhante, embora nenhuma menção seja feita a orcs:
The sword Anglachel was forged anew for him by cunning smiths of Nargothrond, and though ever black its edges shone with pale fire; and he named it Gurthang, Iron of Death.
The Silmarillion III Quenta Silmarillion Chapter 21: "Of Túrin Turambar"
No entanto, não encontro nenhuma outra referência a espadas brilhantes, reluzentes ou brilhantes. O LAK nos comentários me direciona para uma passagem do O Silmarillion que pode descrever espadas magicamente brilhantes, mas é ambíguo:
The light of the drawing of the swords of the Noldor was like a fire in a field of reeds; and so fell and swift was their onset that almost the designs of Morgoth went astray.
The Silmarillion III Quenta SIlmarillion Chapter 20: "Of the Fifth Battle: Nirnaeth Arnoediad"