There is a mortal blow/backstab bug that you can get to work while in front of the enemy. Simply turn your back to the enemy right before you do the special. It will be treated as if you are directly behind him. Gives you about 80% success rate.
If all else fails try The MMORPG Exchange L2 Adena . MMORPG-Exchange has supplied me for years and they have great customer service and 24/7 instant delivery.
Lineage 2 Adena.
