Practice combat, commands and the limits of duel protection.
Use /duel for a single opponent or /partyduel as a party leader. Formal duels last two minutes; a single duel is won when the opponent reaches one HP. A normal defeat has no experience-loss penalty, and the participants' pre-duel HP, MP and CP are restored when the duel ends. /withdraw ends it early.
NPC interference ends a one-on-one duel without restoring those resources. Party duels also have eligibility restrictions, including combat, chaotic status, Olympiad participation and insufficient HP/MP. Formal duel behavior must not be generalized to ordinary open-world PvP.
Have members finish combat and recover HP/MP before requesting a party duel. Accepting removes that party from its command channel and party matching. Choose a location away from NPC interference for a one-on-one duel, and keep the two-minute limit in mind when practising. Normal field combat outside the formal duel does not inherit its resource restoration.