Reclusion and ascetic discipline
After his tonsure, Isaac embraced an exceptionally severe reclusion, shutting himself in a small cell. The accounts of his life stress the rigor of his diet: he is said to have taken only a single prosphora and a little water at the end of each day, while in one recension Saint Anthony passed him a blessed loaf through his cell window every other day.
It was in this extreme solitude, after about seven years, that he met his great trial. The demons came to him in the guise of angels of light, and finally one appeared whom he took for Christ himself; deceived, Isaac worshipped him. The deception broke his health: he was left crippled, unable to walk or speak.
Restoration and holy foolishness
Saints Anthony and Theodosius, the founders of the monastery, tended Isaac through his long incapacity, and over the course of about three years his strength, speech, and movement gradually returned. The OCA life relates that he was at first reluctant even to come to church and had to be brought.
Upon his recovery he took up the exploit of foolishness for Christ, enduring beatings, nakedness, and cold; he is counted among the early fools-for-Christ in the northern Russian lands. In his later seclusion the demonic assaults returned, but by the Sign of the Cross and by prayer he overcame them, becoming, as one account puts it, a cautious and experienced ascetic.
Relics and veneration
Isaac's relics repose in the Near (St. Anthony's) Caves of the Kiev Caves Lavra, among the venerable fathers of that monastery. A portion of his relics was transferred to Toropets, his native city, in 1711. He is commemorated on February 14.
