Method to Acquire: Speak to him with Lugh on Chapter 12. If your Lugh is on a low level, make sure all the Fighters and the Warrior near Rei are dead the move Lugh right at the edge of Rei's movement and then have Elphin or Lalum make him move again to speak with Rei.
Damage - Rei's damage is incredible. He'll probably gain Magic at every level or every other level making him devastate enemy units.
Critical - Unfortunately, Rei doesn't have a high critical. He doesn't need one though, as he deals a lot of damage.
Speed - He's very fast for a Shaman, and he can destroy enemy units with two attacks if they manage to survive his first.
Dodge - His dodge isn't all that great but you can purchase Nosferatu spellbooks in a few chapters, so he'll gain every hit point back from his enemy.
Growth Rates
HP - 55%
Magic - 45%
Skill - 55%
Speed - 40%
Defense - 15%
Resistence - 35%
Luck - 15%
Averages Level 20 Druid Rei(Does not recieve a Hard Mode bonus for some reason...)
HP - 41
Magic - 28
Skill - 24
Speed - 22
Defense - 11
Resistence - 21
Luck - 10
Total - 157
Supports
Lugh - 14/20/33 turns
Chad - 30/30/40 turns
Hugh - 55/60/80 turns
Niime - 59/60/80 turns
Sophia - 59/60/80 turns
Rating - 9.1/10. Simply put, Rei is amazing. He's your best bet against Mamkutes once he's a level 5-10 Druid because he can survive one hit and he'll take back every hit point with Nosferatu and doesn't waste a Divine Weapon.