"they came like angels out the unknown"

"an unknown amount"
"an unknown island"
"an unknown writer"
"an unknown source"

"a poem by an unknown author"
"corporations responsible to nameless owners"
"an unnamed donor"

"things obscurely felt surged up from unknown depths"

"an obscure family"
"unsung heroes of the war"

"used many strange words"
"saw many strange faces in the crowd"
"don't let anyone unknown into the house"