Flaming

Flaming brands allows weapons to burn when they hit, inflicting bonus damage on victims without fire resistance, even more if they are especially vulnerable to fire (such as ice beasts). A weapon with this brand will burst into flame when wielded, identifying it.

Tips and tricks

This brand is extremely useful for sharp weapon users when fighting hydras, as it will prevent them from growing extra heads when the sharp weapon hits them.

This brand is best on a high-damage weapon, since the damage is multiplicative.

Weapons can be temporarily given this brand with the level 2 spell Fire Brand.

Flaming weapons can be obtained from a number of sources. Certain monsters such as efreets and fire giants are reliably generated with them, as are a few uniques such as Erica. They are also fairly common in the Elven Halls, and can be found in the Hall of Blades. The spell Fire Brand applies a temporary version.

Source code

Damage Spoiler:

• Not fire resistant or susceptible:
  • +25% damage on avg.
• Fire resistant (1 level):
  • +12.5% damage on avg.
• Fire resistant (2 levels):
  • +5% damage on avg.
• Fire resistant (3 levels):
  • +0 damage
• Amount of damage is reflected by punctuation at the end of message:
  • 1-2 "You burn ... ."
  • 3-6 "You burn ... !"
  • 7 and more "You burn ... !!"

Source:http://www.crawl.webpark.pl/melee.html

The extra damage ignores monster AC, which can be useful, although admittedly it is most powerful on high-damage weapons which are already good at penetrating AC.