Board Thread:Card Unit Builds/@comment-99.67.86.19-20141107010938/@comment-25151790-20141110194014

I think what the person meant was that Jack O' Lantern has 2 procs - as in her skill can activate twice per battle.

You can still upgrade a max level card with N cards and ATK/DEF arcana. You won't gain any levels, but the arcana will still increase ATK/DEF.