Firstly, use powder of fortification (you may already know this but I have to say it regardless)
Then you have to consider what your character needs. Could be any of the following:
Hit chance increase
Swing speed increase
Hit mana leach
Hit life leach
Hit stami
Damage increase
Besides those, hit lower defense is a popular option. Could also consider hit lower attack. Probably depends on the mob if you choose one over the other but I think HLD is the more common option of the two (someone correct me if I’m wrong).
If you decide to target a specific mob, you may want to consider making it a slayer weapon.
I would not use any hit area effects as this weapon having armor ignore means you’re going to be using it to destroy single targets.
Whatever your choices end up being, you should maximize the cold damage output of this weapon by enhancing it with agapite which would give it 30% cold damage and 20% energy damage (as per this page
Material Bonuses – Ultima Online ) I recommend using a forged metal of artifacts tool from the UO store to guarantee success and not losing the item.