Taking a deity as your patron
You can bind to a god (or: take a deity as your patron god) if you meet the alignment requirements. Everybody can bind to a god, and pray to it, but Clerics get the best mileage out of it. You can bind to a god in two ways:
a. You search for its idol in the game. Click on it to open a conversation which allows you to bind to it if you have the right alignment.
b. You enter the deity's name in the deity field on character creation. Mind that the deity will fry you if you pray without meeting the alignment requirements.
I'll use Nicholas the Maniac ( Level 7 CE Cleric, domains Magic and Destruction ) who has bound to Cyric as an example.
NB: You may reconsider your faith until reaching level 10, ie, you may choose a new deity before you hit level 10. After that, deities can only be changed with DM assistance (and a bloody good RP reason; deities don't fancy people swapping them like socks!).
You can pray to your patron once a RL hour. Non-cleric characters have a 40% chance to gain a personal blessing. Clerics always get a party-wide blessing (as long as the party members are in the same area). The aformentioned blessings are based on your alignment. Clerics get an additional party-wide bonus if they have domains that match their patron's portfolio.
Druids that follow a god with Animal or Plant domains will act like Clerics and give an auto-success party -wide alignment blessing. They do not get any domain blessings (as they obviously don't have a domain).
All other characters add twice their Paladin, Rangers, Blackguards and Champions of Torm levels to the 40% base success rate. A level 30 Paladin would thus get an automatic success.
The duration of a prayer is 5 turns + 1 turn / 3 Cleric (or Druid) levels. This equals 5 minutes + 20 seconds for every Cleric level.
Nicholas' prayer would thus last 7 minutes and 20 seconds.
The prayer is accessed from the Rest menu. This effectively means that you cannot use it in the thick of a fight.
Alignment based blessings
You get a +2 dodge bonus vs the opposite alignment on the Good-Evil axis. Neutrals get a +1 vs both Good and Evil. A further +1 is added when you have 10+ Cleric levels. Nicholas is Evil and gets +2 vs Good. He'll get +3 vs Good when he reaches his 10th Cleric level. This bonus is given to himself AND party members in the same area because he is a Cleric.
Domain based bonusses
See Deity Domains for details.
 Deity System