PLEASE ANSWER!!!! (nintendo DS, Avalon Code, Light Code?)IN NEED OF DESPERATE HELP!!!?

Please. I'm fighting an invincible goblin or hob goblin or whatever. Its weakness is light but I only have one. Please tell me where I can get more, or of one light is enough, what other codes do I pair it with. Please help. I'm begging you guys. I'm desperate to get past this level. Please and thank you!