Orcs are not a race. Orcishness is an affliction that will sometimes happen to groups of people. It spreads like a strange disease, but many of its sufferers do not care to be cured.
What happens when you're Orcish:
- Gain Darkvision to 6"
- Gain a 1d6 melee attack barehanded
- Fight and Save as a Fighting-Man of your level
- Speak a cool new language
- Really please the ladies without even trying very hard
- Become completely incurious. Lose all casting abilities
- Get -1 to all rolls in daylight or bright lighting
- Your stats are set to S 16, I 5, W 5, D No Change, Co 16, Ch 5. So if you depend on mental stats, you're doomed.
How to become Orcish: Spend a week with a community of Orcish people. After the week, Save vs. Poison. If you fail, you will start to become Orcish. You cannot choose to automatically fail this Save. You will become quite strong and vigorous, then slow and stupid, then turn greenish and your teeth will protrude. You will forget your old personality and prefer orcishness in most cases.
How to stop being Orcish: Spend 70 GPs per character level and live for one month with a religious order. They will lock you up and cure you, much in the same manner as they could cure someone suffering from lycanthropy. Alternately, allow an apothecary and four strong men to heal you over the course of the month - it does not require clerical magic per se. Rates and success vary.