Theic and pantheic were both unknown to me. It turns out they're not actually related.
A theic is someone who drinks excessive amounts of tea. A pantheic is NOT someone who drinks excessive amounts of many kinds of tea. It's an adjective, originally describing a statue featuring attributes of many gods. It has come to mean more generally, relating to many gods.
Pantheic is a very rare word. It's listed in the (19th century) Century Dictionary and in the OED, but not in any other dictionaries as far as I can see. Still, it is a word, so I'll allow it in future, as a rare word obviously.