Backstabbing lets you stab someone in the back with a piercing weapon. You must #hide first. So to use it you need to have atleast 15 points in hiding and as many as you want in backstabbing. The strength of the backstab is determined by how much backstabbing skill and piercing skill you have. It is not really effective against bots because they are difficult to get behind. It it best used on afk players.
Steps to use:
1. #hide
2. Go behind someone with a piercing weapon.
3. Attack!
If you hit them it will say something like "You backstabbed x for x damage!". You will then need to #hide again before you can backstab again. You will also need to #hide again if you miss.
I think that covers it.