I prefer sanctuary and ace guard but both of em are sometimes very hard to use...
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1.Sanctuary-Noon only,thats crap cause at last all the battlefields are set at NIGHT.Good for early battlefields only.
2.Ace Guard-OhMaGah 4 Mov!! Good if you fighting a stucked battle. Exp:Paltina castle takedown and while saving Yggdra.
But,Bloody Claw and Chariot also good.
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Bloody Claw for assasins
Chariot for Knights when only leader left. Yay 1-1....(When I went crazy,I choose Durant and FIGHT all the enemy using this card 1-5 unions and voila!! All wins and get a hefty bunch of exp.