Thor, Vol. 1 #148 (1967) 1st app. The Wrecker, Origin of Black Bolt

Let There Be...Chaos! / And Finally...Black Bolt!
Let There Be... Chaos! - Odin's wrath has come down upon Loki, Thor, Balder and Sif alike, stripping them of their enchanted abilities. Loki abandons the other three, and attempts to gain his power back with the aid of the Norn Queen, only to find his requested power sent to a criminal called the Wrecker instead.

...And Finally: Black Bolt! - Agon and Rynda are two prominent Inhumans, whose genetic experiments have given their son incredible power. They soon realize that such power is too much for an infant to safely bear.
Release Date: 1967