what religion would cover these beliefs?

A belief in multiple Gods, particularly 'nature' Gods, but also in evolution
A belief in reincarnation - as animals or people
A belief in an underworld and devil

Can you think of a single faith or religion that these beliefs could all belong to?

Buddhism.

hinduism for the top two
and Christians believe in the devil

***Buddhism.***

Uhhh no... Buddhism is an atheistic religion.

it sounds very much like christio paganism/satanism and hinduism
the top two are pagan/hindu the belief in many gods, nature spirits/gods and reincarnation, agree with evolution just because we evolved doesnt mean there are no gods
but pagans/hindus do not believe in satan
both paganism/hinduism by biblical definition are classed as pagan, but there varying opinions on this then there are thesistic satanists believe in the devil but there is also an athiestic branch of satanism

pagan panthism sees the gods as architypes and not actual beings just facits of human nature they donot beleive in the devil or an underworld
then there is christopaganism which uses a pagan worshiping system and christian deity/saints

I would sujest going to this website
http://www.beliefnet.com/Entertainment/Quizzes/BeliefOMatic.aspx
answer the questions as honeslty as you can this will give you an overview of your beliefs and give you a % on your best match... then its just research im afraid...good luck on your path
you need to be more specific in your question, what or whom do you mean by the devil there is an underworld in many of the pagan beliefs example hellenism where hadies resides or egiptian after life with osiris.
are you refering to the christian depiction of the devil or is that the only name you know to decribe an underworld being?