Rowan's consciousness passed through the long stretch of decimated undead and the unlucky mages or demons who were struck by the cannons; he could feel his pile of Soul Crystals swell up from the death of hundreds of millions, including dozens of Soul Mountains.
This wave of destruction had reminded him of Telmus, each of these cannons could be said to be a Mini-Telmus, capable of unleashing a potent wave of destruction with a single move using Intent as its vehicle, although it lacked the sheer control needed to weave all this destruction in a focused direction, leading to a wide dispersal of its energy, it was still more than enough to kill even a Demon Prince and any Immortal below.
Originally such a blow should do nothing but shatter their bodies and would be nothing but an annoying inconvenience, inside his dimension, every death was permanent.