During the initial test of the Instrument of Doom, its full-powered blast managed to pierce through sixteen or so asteroids before it could penetrate no further.
Though the test was anything but rigorous due to the considerable variations between asteroids, it was still a clear sign that the penetration power of this weapon was unreal!
However, nothing came for free.
The Phase King had to cooperate with Venerable Stark and the Amaranto to channel a considerable part of his energy to the attack.
Doing it once or twice was not a big deal, but the more the design spirit had to exert his power, the more strain everyone incurred.
Design spirits existed in a different realm and were not meant to affect the material realm to such an exaggerated degree.