Hit by infrasound

The Outsider’s tentacle cluster swept toward Ebenezar, quivering wildly, and though I couldn’t hear anything, the air shook like the speakers at a major concert, the air around them rippling with something that looked like summer heat waves on asphalt.
The edge of that cone of quivering air emanating from the Outsider’s tentacle face brushed against my grandfather. The old man sucked in a short huff of surprised breath, staggered, and collapsed.
Sudden terror for my grandfather crashed over me, mingling with my frustration and rage from moments before, like gasoline being mixed with petroleum jelly.

Peace Talks Chapter 11, Page 92


I staggered, suddenly dizzy and weary from throwing the three energy-intensive spells back to back. I stumbled and had to lean on my staff to keep from falling, but I made it to Ebenezar’s side and helped him sit up.
“What happened?” I asked him.
His voice came out rough. “Infrasonic attack. Like a tiger’s roar. Super-low-pitched notes, below what humans can hear, capable of making your organs vibrate. Can have a bunch of effects …” He blinked his eyes several times, owlishly, and then said, “Hell of a thing to try to stop. Help me stand up.”
I did, drunkenly. “How tough are these things?”

Peace Talks Chapter 11, Page 93