Code:
Damage(Mob* from, int32 damage, uint16 spell_id, SkillType attack_skill, bool avoidable = true, int8 buffslot = -1, bool iBuffTic = false) = 0;
$npc->Damage($h_ent, $h_dmg*0.1, 0, 1, true, -1, false);
Heres an idea of how to use damage. Be aware its very dangerous to use as you can cause crashes with it if you try to Damage a null entity.