Quote Originally Posted by Calthropstu View Post
A372 rebuttal: The requirement simply states it requires 120,000 gp and must be crafted by the lich himself.
Nothing says it cannot be imbued with more magic than just the phylactory, and mythic legendary can be imbued into anything...
So wouldn't it be possible so long as the item was crafted by the lich himself?
Alternatively, couldn't the lich take the phylactory as his legendary item?
The Lich template and the Phylactery item and the creation of both are linked. You can't have the one without the other. The phylactery entry states that this is an example form and other forms are possible, but excludes other items (and also doesn't got into it what happens when you take an pre-existing magic item or a Bonded Object).
So, as this is the RAW thread, "no" is the RAW answer, everything else is "ask you gm" (The Mythic Lich does it, but the template doesn't come with rules how to become one and transform the phyactery)