What is the best obtainable Magic Tome in Fire Eblem Radiant Dawn?

Hiya, I love Fire emblem RD and I had on a wii like 3 years ago and played the heck out of it, but my bro sold the wii, so the data went. Anyways its been awhile and im sleeping over my friends house and he has it, and were gonna play it like all day. I know how to get Shephiran, (were planning to beat the game in a day) and I wanted to know what the best magic Tome would be for him Cuz I know he doesnt have creiddyald with him when you get him... He only has Ashera's Staff.. So what would be the best magic that I could get for him. He can use any type so what magic tome, and where do you get it.. Thanks. PS im getting Pelleas too, so what is a good one for both of them Thanks!