Here's a draft house rule for you, hope it helps.
Making Magic Potions
New skill: Alchemy (base 00%). Training costs 2,000 sp per 5% increase.
Alchemy can be used to embed Battle/Spirit Magic spells into liquids. The caster must know the Battle/Spirit Magic spell and have the ingredients available.
The ingredient costs are figured according to the following table:
1-pt spell: Common ingredients (found in most large marketplaces) costing 25 sp.
2-pt spell: Common ingredients (found in most large marketplaces) costing 50 sp.
3-pt spell: Common ingredients costing 100 sp, plus an uncommon ingredient the player must find (e.g. griffon feather, mummy wrapping, troll tooth, etc.)
4-pt spell: Common ingredients costing 200 sp, plus three uncommon ingredients the player must find.
5-pt spell: Common ingredients costing 500 sp, plus one rare ingredient the player must find (e.g. giant's toenail, dinosaur eyeball, phoenix feather, etc.)
(etc.)
Manufacturing the potion costs twice the amount of temporary POW as the spell imbedded would cost to cast. Thus to cast a 2-pt healing potion would cost 4 points of temporary POW.
The potion takes effect 1d20 strike ranks after being consumed.
If subsequent potions are consumed by the same person on the same day, there is a cumulative 1% chance that the magical liquids will become toxic, causing the drinker to be affected as if by a poison of 1d20 potency.