# When a creature's type changes to undead, what happens to its hit points?

When applying a template like necropolitan (Libris Mortis 114-5) that changes a creature's type to undead (and its Hit Dice to d12s), does the creature's hp total change retroactively due to its new HD and (likely absent) Constitution score?

For example, if a living wizard's Constitution penalty affects his hit points, is that penalty removed if he gains a template that makes him undead?

• I removed the dead link, using a page reference instead. While I was doing that, I tried to clarify the question. If that's too extreme, please roll it back or edit it further. – Hey I Can Chan Aug 10 '16 at 16:22

Thus, for example, a PC wizard with 12 Hit Dice and a Constitution score of 8 would normally have 4+11d4−12 hp (that is, on average, less than 20!). But, when that PC wizard gains the type undead and its Constitution score becomes —, the wizard has 12+11d12 hp (about 83 hp!). (Note that while monsters don't get maximum hp on their first Hit Die, PCs do.)