Trail of Blood (3.5e Feat)
From D&D Wiki
Trail of Blood [Epic]
You're obsession with slaughter allows you continue the spilling of blood.
Prerequisite: Dex 21, any evil alignment,Mobility, Power Attack, Great Cleave, base attack bonus +21
Benefit: If you deal a creature enough damage to make it drop (typically by dropping it to below 0 hit points or killing it), you can immediately move up to your movement speed and make an extra melee attack as a free action. This movement doesn't count against the speed you are able to move at each round. The extra attack is with the same weapon and at the same bonus as the attack that dropped the previous creature. If this enemy is slain, the process continues. Each one of your extra attacks from your base attack bonus can trigger this feat.