Basically, when a dopple clones you when you are NOT morphed, there is no border. It looks *exactly* like you, and you have to hit Ctrl to kill it. However, if you do morph first, and it sees you in morph, not only does it become your morph, but you can see a faint border around the name. (Linspatz also wanted to point out that you DO NOT need to hold down Ctrl to kill a dopple in a morph, but only if the morph is into a monster. Morphing into a milkcow, for example, still requires you to hold down Ctrl). With this, we were able to determine that a doppleganger is level 18. The use of a mana staff showed us that a doppleganger has 30MP, and killing it showed us that a dopple has 25 lawful.

Some crude experiments with vampiric touch told us the dopple has around 300HP, but we're not sure, so we didn't put that in. We're also not sure of its AC, but its probably the same AC as other level 15-20 mops.

I added what we are certain about dopples to the Monster Guide.