I don't know if they changed in Lineage 2 Classic, but since prelude the game used the next formula: xp_member1=lvl_member1^2 * total xp / (lvl_member1^2+lvl_member2^2....) So an example would be: mob gives 10000 xp solo, 2 man party of a lvl 40 and a lvl 45. 2 man party, so mob gives 1.3 times xp -> 13000 xp 40^2=1600, 45^2=2025 the lvl 40 gets 1600*13000/3625=5738 xp, the lvl 45 gets 2025*13000/3625=7262 xp And the penalty beetween the monster and the exp recieved is calculated from the High Lv. charater and not for every character of the party.