I believe the radiant that Dalinar sees in his vision of the Purelake is a Releaser.
Reason 1: The radiant starts surgebinding then cuts through the water like it's not there, suggesting the surge of abrasion.
"She raised her shardblade and charged, stepping through the water with uncanny ease, as if it had no purchase on her"
Reason 2: is summed up by this old post:
This assumes that the gems from the chart of 10 essences do in fact match up with the gems in a radiants shardplate. It has been confirmed that Windrunners glow blue which matches sapphire and Stonewards glow amber which I believe lines up with topaz.
Reason 3: The Knight should of one of the warrior orders.
Reason 4: The Knight should be equipped to deal with a Thunderclast, as the spren bringing "an escort" sounds like it's not totally unheard of and therefore would have been planned for.
The surge of abrasion points to the Radiant being either a Releaser or an Edgedancer, and the red shardplate points to Releaser or Lightweaver. Therefore I believe the radiant in question is a Releaser, reason 3 and 4 are less definitive but also line up with the theory
