Is there a way to give constitution to a creature that does not currently have one?

[Nightfox1]

There are several abilities (both beneficial and detrimental) that only work on creatures with a constitution score. I'm trying to find a way (spell, magic item, etc.) to give a creature (like undead or constructs) a constitution score. It doesn't have to be permanent, or even "real", I just want my character to be able to interact with them as though they had one.

A Belt of Mighty Constitution gives an enhancement bonus to Con, but if the Con is "-" does the belt just not function, does the Con just magically become 2, or is the Con now counted as 12?

What about a Manual of Bodily Health?

I feel like there has to be a feat or spell that would allow you to treat such entities as though they have one, even if they are still immune to most of the effects that would come with it.

[Secret Wizard]

For undead: https://aonprd.com/OccultRituals.aspx?ItemName=Blush%20of%20Youth

For constructs: https://aonprd.com/ConstructMods.aspx?ItemName=Bioconstruct%20Modification

[Nightfox1]

Secret Wizard wrote:

For undead: https://aonprd.com/OccultRituals.aspx?ItemName=Blush%20of%20Youth

For constructs: https://aonprd.com/ConstructMods.aspx?ItemName=Bioconstruct%20Modification

Thank you. I'm not sure if these would work but they are very interesting. Both appear to be based on reforming the subject somewhat, and I'm not sure if I'll be allowed to do any form of permanent change to the other players characters, or DM's NPCs. The goal is more to allow them to be targeted as though they had a con score, hopefully without them having to give up most of their natural immunities for allies, or requiring them to stand still for extended periods of time while rituals and modifications are performed for enemies.

[Dave Justus]

The belt and book wouldn't do anything. There may be some specific character/class abilities or feats that allow you to do what you want, but it isn't clear exactly what it is you are trying to accomplish.

Perhaps you would have more luck if you tell us specifically what you are trying to do.