sky130 is a triple well process so there is a pwell which isn't psub. The pwell sits inside a dnwell

Yeah, technically that is correct. But there is no "pwell" layer. There is only psub. Its just the psub of one section can be isolated from other psub using dnwell and nwell. In the context of the cells generated by the Magic, they cant have pwell, because there is no such layer and dnwell is out of the picture since magic does not generate one as far as I remember. I was just trying to point out the fact that users should not expect layer called pwell in the gds.

Absolutely, I understand where you're coming from but just wanted to point out that there is a pwell. But your point does raise one of the reasons I don't use magic. I don't like it hiding the GDS layers, in KLayout you can directly see and control the layers you're sending to fab. Incidentally there is a pwell layer https://skywater-pdk.readthedocs.io/en/main/rules/layers.html#gds-layers-information But it's used for resistors

So, this "background concentration" is the Np of the p-substrate, what about this pwell concentration? Also, how would the layers be if I wanted to do a triple well isolation using dnwell? I confess that I got confused now hehehe

Use magic to generate it. Essentially you need 5 sides of nwell. The dnwell is the bottom layer isolation, nwells + dnwell on four sides are used to isolate the psub from "pwell".

Speaking of shady layers... the hvtr (high Vt RF transistor) seems interesting :^)