Nityavibhuti or Shuddhasattva is the transcendental matter in contrast to the prakriti that is the cosmic matter. It is a spiritual substance characterised by pure sattva unlike the physical matter which constitutes three gunas. It is non-material and insentient. It is classified under the parak and hence it illumines everything but does not know. Visistadvaitins accept shuddhasatta category since Agamas maintain that idols that are consecrated is permeated with shuddhasattva thus making the place of worship a spiritual sanctorum. Moreover, the bodily form of Ishvara cannot be made of cosmic matter that is subject to origination and destruction, but it is made of shuddhasattva. However, Ishvara is the controller of and substratum of both the prakriti and shuddhasattva.
(Source: BPY005/Block 2/Unit 3/Page 35)