Caeso looked at the dark-red energy entering his body. At first, he felt nothing about it, less than three seconds later he felt the reaction. His Void Energy revolted, fighting the foreign energy inside his body. That was a normal reaction when a foreign energy was forcefully injected into his body.
However, that was not the end of it. The foreign energy was much stronger which resulted in an even more violent reaction to his body. He felt like the flesh inside his body was torn apart by the clash between the two energies.
He felt like his bones were getting crushed, grounded by the clash. The Void Energy and his energy pool went berserk, uncontrollably. But that was futile because his Void Energy was eaten by this foreign energy.