Emperor Vek'lor and his brother Emperor Vek'nilash comprise the Twin Emperors boss encounter inside of the Temple of Ahn'Qiraj.

While no strategy is needed anymore, it's important to remember that they need to be tanked at opposite sides from each other or else they will heal each other. Every 30-40 seconds they will teleport to switch places and drop aggro. If DOTs or other abilities are up on them, they may start running back to their original place from which they teleported which will cause them to be near each other and potentially heal.

A good strategy is to have one person take each one and put up abilities that damage over time on their respective target. That way, when they teleport, they will have the DOT tick and run back to their original tank. This strategy means they will heal, but it is negligible with level 85 DPS.

This NPC can be found in Temple of Ahn'Qiraj.