Cocytus: "...Your opponent cannot target this card with card effects..."
Herald: "...Your opponent must send 1 face-up monster with the declared Type and Attribute from their field to the GY, if possible..."
How come the The Herald sends the Cocytus to the GY?
They aren't going to touch Invokeds because the deck is not even Tier 1, but tier 2. Not overpowered.
NEW BANLIST UPCOMING FEBRUARY 4th
COCCYTUS 1 TO 2
INVOCATION TO 2
Your comments are Malicious and Harmful
The keyword is "TARGET". When a card doesn't use that word (e.g. Herald) it will bypass the effect of Cocytus and other cards.
Herald's effect didn't "target", so yeah it can sends Cocytus to the GY since Cocytus only immune from effects which has 'target' in its text.
It's like how Cocytus can be banished by Fortune Lady Every since its effect don't have "target" text.