aparently all cards are stackable (best ones i found for wizard):
ring crawler = 10 int
rexifer = 10 m amp
chapparition = +10% matk 10 sec after SP Pot
helgasercle = 10 matq
yeti = 1200 hp
blud = 10 con
manticen = +10 mov speed stampot
dullahan = 5% ress 10%hp chance
spector gh = +10% SP pot effect
reaverpede = +10% damage medium size (player)
kubas = 1% sleep chance on magical attacks [EACH CARD]
these thoughts on stackable or not come from the fact that some cards have star counts and other number counts. Also there are some who would be too op if stackable.