The Aura of the Explorer that was killed was purified, and as it rushed into the body of the Shiik, headed for the core of its power which was the rune resembling a withered hand, Rowan halted it in place, before diverting it towards him.
Although the growth of Aura did not depend on the type of Aura it consumed, whether from Calamity or Ascendance, for Rowan's future plans to work, the energy of the Shiik must be kept pure, which means any Aura it absorbed must come from Calamities… Rowan on the other hand would be feeding on the energy of Ascendancy.
The Shiik had never killed an Explorer before and so although its body was filled with Aura to a bursting point, the Aura was all the red of Calamity.