From 1512 to 1514 or 1515 he worked on the Isenheim altarpiece, apparently in partnership with another Mathis, variously surnamed Nithart, Neithart, von Würzburg (after his place of birth), or Gothardt. Grünewald seems to have left Isenheim in a hurry, returning to Frankfurt, and his subsequent poverty suggests he was not fully paid for the altarpiece. In 1527 he entered the services of the wealthy and noble von Erbach family, apparently with a child (whether his own or adopted, is unclear). He most probably died in 1532, although sources vary.