The Soul of Vaikundar is that of the Paramatma or the Ultimate God, (see:Ayya Vaikundar) and it was viewed that the Ultimate God or Ekam (the God beyond Consciousness), incarnates here in the world.
Immediately after the ceremony of avatar of Vaikundar, Narayana called Vaikundar "Your self is Sivan, your self is Vethan, your self is Thirumal and your self is the austerity, your self is Brahman and your self is the whole which exists."