Charles Spurgeon Commentary 2 Chronicles 33:5-6

"And he built altars for all the host of heaven in the two courts of the house of Jehovah. He also made his children to pass through the fire in the valley of the son of Hinnom; and he practised augury, and used enchantments, and practised sorcery, and dealt with them that had familiar spirits, and with wizards: he wrought much evil in the sight of Jehovah, to provoke him to anger." — 2 Chronicles 33:5-6 (ASV)

And he built altars for all the host of heaven in the two courts of the house of the LORD. And he caused his children to pass through the fire in the valley of the son of Hinnom:

Perhaps he gave some of them actually to be burned in honour of his false gods; or if not, some of his children were made to pass through the fire and were thus dedicated to the idol deities.