Disguise Form

Disguise
This form made Kain look like a human peasant. He could move through towns without attracting the attention of the guards. He could also talk to humans, who sometimes gave out information about the area. Kain was unable to attack while in this form.

Beguile
This was a better version of Kain's Disguise form, allowing him to appear as a human nobleman. Kain needed Beguile form to speak with King Ottmar of Willendorf. It didn't change Kain's body physically, it simply altered people's perception of him. If Kain attacked someone while using Beguile form, the spell was broken.

These two forms have the same purpose & in Blood Omen 2, Vorador mention's Kain's ability to " mask [his] presence. "