clif_damage(struct block_list* src, struct block_list* dst, unsigned int tick, int sdelay, int ddelay, int64 sdamage, int div, enum e_damage_type type, int64 sdamage2)
src : who send this
dst : who receive this
tick : when do this
sdelay, ddelay, div, sdamage2 : you don't need to care it
sdamage : yeap, damage number
type : 0 ~ 12, there are info in clif.c
Here is a little sample about monster send 9999 to me :
clif_damage(&md->bl, &sd->bl, gettick(), 0, 0, 9999, 0, DMG_NORMAL, 0);