And, as any proper nerd knows, the only way to assuredly get rid of a troll is to hack it into smaller bits and light them on fire.
"Trolls are infamous for their regenerative abilities, able to recover from the most grievous of wounds or regenerate entire limbs given time. Severing a troll's head results merely in temporary incapacitation, rather than death. After cutting off a troll's head or other limbs, one must seal the wounds with fire or acid to prevent regeneration. Because of this, most adventurers will typically carry some sort of implement capable of creating fire."