Thor, Vol. 1 #149 (1967) Origin of Black Bolt, Origin of the Inhumans

When Falls a Hero! / Silence or Death!
When Falls A Hero! - Loki has engineered it such that Odin is unable to observe Midgard and learn of the deadly battle Thor is fighting against the Wrecker. Balder and Sif gain permission to go to the Norn Forests in search of Loki, but they may not get there in time.

Silence or Death! - Black Bolt has reached the age of nineteen, having been raised in a soundproof chamber. It's time for him to leave with his cousins, though his brother Maximus is determined to prove that Black Bolt should never be free, and thus never be heir to the throne.
Release Date: 1967