|A Temple of the Gods, a place of peace and refuge from the insanity of the dungeon. It usually contains altars to most of the known gods. It is located between the levels 4 and 7 of the main dungeon.|
The Ecumenical Temple, also known as the Temple of Gods, is the first branch of the Dungeon most players will encounter. Located somewhere on Dungeon:4-7, it contains altars to multiple gods, but nothing else.
Entering the Ecumenical Temple is entirely optional, but if you started the game with a non-religious background, it's a good place for choosing a god. You can learn more about each god's religion by standing on their altar and praying (command p).
Monsters never randomly spawn in the Temple, but they can follow you or be created there (via a god's wrath, a miscast effect, or your own spell). Certain layouts may also have monsters in them, but they are always sealed off behind transparent walls.
The Temple has a single floor randomly picked from a predetermined pool of layouts. Whichever layout is picked, you'll find altars to at least six gods, but usually more. Any gods who are not represented in the Temple will have an altar somewhere between D:2-9, with three exceptions.
The Temple will never contain altars to Beogh. It can very rarely contain altars to Jiyva or Lugonu, but each has a special layout for the temple that is "corrupted" by the god in question, which replaces most of the other altars. You can find these three gods in certain branches (Beogh in the Orcish Mines, Jiyva in or near the Slime Pits, and Lugonu in the Abyss). Both Jiyva and Lugonu can also appear in rare dungeon vaults.
If the Temple's entrance appears to be unreachable, try to get in via an unused set of stairs on another floor.
Most gods are guaranteed to have an early altar present here. If an altar to a deity other than Lugonu, Jiyva, or Beogh is not found in the Temple, it will be found somewhere between D:2-9. Such altars are called overflow altars. Note that not every altar you see in that range is necessarily an overflow altar, although most are.
Also be aware that while altars to Lugonu, Jiyva, and Beogh are not normally found in the early game, hill orcs can convert to Beogh upon encountering an orc priest, while any race can start with Lugonu by playing an abyssal knight. Thus, the only god who is difficult to pick up early on is Jiyva.