The Encyclopaedia of Religion and Ethics is a 12-volume work (plus an index volume) edited by James Hastings, written between 1908 and 1927 and composed of entries by many contributors. It covers not only religious matters but thousands of ancillary topics as well, including folklore, myth, ritual, anthropology, psychology, etc. It was originally published by T&T Clark in Edinburgh, and Charles Scribner's Sons in the United States.
Several volumes are available from Google Books in "full view" mode. The first few volumes are available from the Internet Archive. It was reprinted by Kessinger Publishing in 2003, divided into 24 volumes without the index, available from Google Books in "limited view" mode. Varda Books has also released an online edition (requires registration to view, requires payment to download).