I put it into Wikipedia on Google and got a Wiki entry in Latin of the book of Job. The words "Quis est iste" started out the sentence. After that, I googled "venit" and found it to be a third-person usage meaning "to come." Thus, "Who is this coming?"
Apparently, it's also the title of a chorus piece:
http://www1.cpdl.org/wiki/index.php/Quis_est_iste_qui_venit,_C._39_(Giovanni_Gabrieli) --- No hay banda! There is no band! It is all an illusion. ~The Magician