Dragonslayer Spear

In-Game Description
Cross spear born from the soul of Ornstein, a Dragonslayer guarding Anor Londo cathedral. Inflicts lightning damage; effective against dragons. Two-handed thrust relies on cross and buries spear deep within a dragon's hide, and sends human foes flying.

Availability
To create Dragonslayer Spear you will need a spear+10 and Ornstein's soul. After, Talk to the Giant Blacksmith and have him craft it.