I'm looking to make a Lich as unkillable as possible, so I'm thinking about taking the existing spell deathward and changing its effect from negative energy and death protection to positive energy and life protection. Seeing as this is a spell with a duration in minutes, I think this is fairly balanced and wont break the encounter too much. but seeing as I could be wrong I implore you, the community to tell me. Is it balanced or gamebreaking?
Would it be possible to make an item out of this or cast permanency on this? how gamebreaking would that be? How much would they cost?
2 things: are you talking about crafting a new spell?
if yes, then maybe a bump, maybe not. {wait... scratch the last}
permancy is expensive in general. starting at 9k+
if just changing the spell for PC's that would be more houserule than rule, if for GM use, then change the name and fiat away.
you can make a magic item with almost any spell