The red tribulation lightning contained the power of destruction, a power that was available for entities at the seventh dimension, but there was a vast gulf between what an average seventh-dimensional entity could unleash when they were wielding the power of destruction and what a realm was capable of.
Especially a realm like Doom Star who although its realm's Will was fragmented, could still unleash potent waves of destruction. It was this pure destruction that was unleashed on the Time Blight.
The wave of red that washed all through the realm was simply the color of destruction, but it shriveled all life that was left on the surface, any Ascendant that was unlucky not to be under the umbrella of any of the two Suns collapsed into ashes, even the massive hourglass representing Rowan's merging dimensions lost a hundredth of its mass before it rapidly regained it back.