U1N1B3E1K5N1O1W4N1S1T1
20 points
UNBEKNOWNST is validvalid
not known (to) [adj]
unknown [adj] / without the knowledge of, unobserved by, also UNBEKNOWN [adv]
not known (to) [adj]
unknown [adj] / without the knowledge of, unobserved by, also UNBEKNOWN [adv]