κρυπτήριος
From LSJ
θεωρεῖται δὲ ἀνοησίᾳ κρείττονι νοήσεως → it is grasped only by means of an ignorance superior to intellection, it may be immediately cognised only by means of a non-intellection superior to intellection
English (LSJ)
α, ον,
A convenient for concealing, ἄντρον Orac. ap. Paus.8.42.6; κρυπτήριον, τό, dungeon, prob. l. in E.Cret.48.