Spamming the Succubus Spell: Lash of Pain on any friendly NPC (Quest Giver, Merchant, Guard, etc.) that has a PvP flag/symbol on it enough times (at any range) will flag you for PvP combat. (Normal / Non-PvP realm).
This can be reproduced over and over.
Does not flag you on friendly NPC’s that do not have a PvP flag/symbol.