where are my souls after being defeated as a black phantom?

Hello folks,

I've just started to try a little pvp in DeS. But I don't understand the rules. I invade an other world and I'm defeated. Then I'm put back to my world and sometimes my souls are gone completely, sometimes I still have them and sometimes they have been reduced. What are the rules here?

Thanks for your help!

Best wishes

I never invaded much, and when I did, I stopped caring about souls because I'd always just kill myself in the Nexus to get back to Soul Form so I could invade again.  To the best of my memory, after being defeated as a Black Phantom, your bloodstain should appear near the same area you were standing when you first received the "Invading another player's world" message.  I could be totally wrong, but it's somewhere to start looking at least 

agree with reaper - if you start to invade, don't care about souls anymore
if you die from environment, your sl is reduced by one. one way of deleveling