After Daniel survived the lions' den, what did King Darius decree?

Answer: All must fear the God of Daniel

Darius decreed that in every part of his kingdom people must tremble in fear before the God of Daniel, for He is the living God.

“I hereby decree that in every part of my kingdom, men are to tremble in fear before the God of Daniel: For He is the living God, and He endures forever; His kingdom will never be destroyed, and His dominion will never end.”— Daniel 6:26 (BSB)