You can become a werebeast only by being bitten by one or angering gods with divination dice and being cursed to assume a form during full moon. Both ways are guaranteed and your disease resistance doesn't matter. Getting clawed or touching a werebeast won't cause infection at all.
If you got cursed or infected during a full moon you won't transform that full moon.
You cannot become a werebeast if you are a vampire.
Being a werebeast grants you biological immortality (removing [MAXAGE] token) while also locking you out permanently from using divination dice for RNG effects.
You won't gain immunity to any diseases by becoming a werebeast but you won't become a vampire.
There is no cure to being a werebeast regardles of how you got infected/cursed.
One massive positive side effect of this condition is healing all your wounds and even restoring lost limbs the very first moment of transformation. All received diseases are also removed. This also works the second way, that is turning back to your original self again.
NPC werebeasts are guaranteed to have level 6 (talented) combat skills in everything and level 15 (legendary) sneaking. The player seems not to receive those bonuses. Any werebeast, even player are immune to pain but only when transformed, otherwise start adventure as a specie who cannot feel pain.
Your attributes both mental and physical are altered in your new form, can be trained normally and don't reset upon becoming a werebeast again. Your attributes of original form remain safe as well.
You are transformed instantly when the game decides to change your form. You remain transformed for way longer than night lasts. You will detransform on next night once moon will no longer be full.