Fantastic work, really inspires one to play "nice" monster party for change.
Hardest part will be to decide what to play...
Btw, really liked the vampire. Brings White Wolf's Vampire the Masquerades blood pool to mind.

Just wondering: there seems to be quit a few monsters that turn you to outsider.

How to get back to material plane?

Not really a problem at lower levels, but at mid and high you are bound to face spellcasters and they will throw dismissals/banishments to your face and thanks to Murby's law, you will fail it sooner or later. How to come back?
Might ruin your hole session if the first clerig send you back to hell and makes you to sit on your seat and be just a watcher, cause you miss all the action.

And really i can't blame DM for doing that: if we would know to expect infernal forces, we - the players, would prepaire to dismiss/banish them.
So it is realistic that opposition prepaires as well, if/when they find out
about your foreign origin.

Any good suggestions beside buying scrolls or other items, cause not every DM lets you buy everything you want?