This is from rAthena src.
case RK_DRAGONBREATH_WATER:
{
int damagevalue = (sstatus->hp / 50 + status_get_max_sp(src) / 4) * skill_lv;
if(status_get_lv(src) > 100)
damagevalue = damagevalue * status_get_lv(src) / 150;
if(sd)
damagevalue = damagevalue * (100 + 5 * (pc_checkskill(sd,RK_DRAGONTRAINING) - 1)) / 100;
ATK_ADD(wd->damage, wd->damage2, damagevalue);
#ifdef RENEWAL
ATK_ADD(wd->weaponAtk, wd->weaponAtk2, damagevalue);
#endif
wd->flag |= BF_LONG;
}
break;
Damage calculation: HP + SP * Skill Level
- Damage depend on base level.
- Damage depend on Dragon Training skills.
My guess Long attack damage modifier and Attack damage modifier will increase damages.
(Seem like Race, Size damage modifier will used in calculation too, since last calculation does plus in left hand, right hand and weapon damage.
I didn't test it maybe just try to increase race, size damage with very high value to test it)