Wielding the Flame of Anor

[Nilpaurion Felagund]

Udûn was also the Sindarin name of Utumno, probably the place Gandalf referred to.

In Utumno, the flames there were used to forge weapons of conquest and carnage. Meanwhile, the flame of Anor is used to give or improve life. It can't harm anything except those who are evil - unless you do something silly.

Which the same for the two rivals.

...for [Gandalf] was the Enemy of Sauron[or the Balrog, in this case], opposing the fire that devours and wastes with the fire that kindles, and succours in wanhope and distress.

(UT IV 2)

...loving especially the beauty of fire; and yet such marvels [Gandalf] wrought only for mirth and delight; and desired not that any should hold him in awe or take his counsels out of fear.

(UT IV 2)

Gandalf's fire is like the sun - never designed to harm anything - except those of the dark.