Any weapon except Dagger will do more damage than an Immortal in the OP deck. Short Sword or, even better, Lobo are the most prudent options for the unupped dude. There's no need to remove an Immortal though, as 15 pillars is more than enough. I personally run 14 (and a SoG) in it and most of my unupped Monoaether decks.