|An enchanted lance deadly to all dragonkind. It grows more powerful every time it inflicts a killing blow on a strong dragon. The more powerful it grows, the harder it will be to find a worthy opponent.|
+8 lance (8 damage, +4 accuracy, 110% speed)
If a dragon slaying-vulnerable target is killed by the base damage of this weapon, it will gain +1 enchantment up to the HD of the dragon killed.
- If you kill a fire dragon (HD 12) with the basic +8 Wyrmbane, it will become +9
- If you then use Wyrmbane to kill a swamp dragon (HD 9), Wyrmbane's enchantment will not change (the dragon was too weak to boost the enchantment).
The maximum enchantment Wyrmbane can gain this way is +18, though there are draconic monsters with higher HD. Even if you manage to kill something like the Serpent of Hell (HD 20) or Tiamat (HD 22) with Wyrmbane, its enchantment won't increase past +18.
A +18 Wyrmbane is a very respectable weapon indeed, given that it provides a high amount of damage with excellent speed (5 min delay). In terms of raw damage it will outperform a demon trident of freezing fairly well, and it isn't too far behind a branded bardiche while requiring considerably less skill investment to start using; it also allows you to use a shield. Moreover, it provides a number of useful intrinsics, many of which can help you survive the dragons you'll have to kill in order to improve the weapon.
The downside is, one must be willing to invest the time spent killing stronger and stronger dragons with it in order to make it a truly competitive weapon. Getting Wyrmbane up to +12 isn't that hard, as you only need to kill fire or ice dragons to get that far, and reaching +14 from fighting storm dragons isn't too much more difficult (provided you have electricity resistance). Past there, though, you'll have to start killing things like shadow dragons, golden dragons, or bone dragons, none of which are particularly easy to find, and which may put up a decent fight.
The Crypt and the Hells tend to send plentiful skeleton and zombie dragons at you, including some of the highest HD ones. These undead foes are much easier to slay than their living brethren, and count as dragons for the purpose of improving Wyrmbane.
Prior to 0.15, Wyrmbane had a +9,+6 enchantment bonus.