Vecna is the god of secrets and lies within the TDDC universe. He rarely interacts with said universe, though, preferring to spend all of his time in the Astral Sea battling with Ioun for control of The Source. He has very few worshippers, but there was at least one poweful cult dedicated to him around the time of the Blood Whip.
Some legends of make the mistake of portraying Vecna as not having a physical form. The truth is that he had a real body, but as the God of Secrets, he was entirely silent and invisible - essentially undetectable. Scholars who know this debate whether other creatures could physically pass through Vecna’s body, or whether other gods could sense his presence under certain circumstances, like when he was close - and wise people disagree on whether or not you could hear Vecna if he willed it so; some say that he could never be sensed, in any way, and it was for that reason that he created the Cloak and Mask which he wore when communicating with other beings.