The Tavern

Both are relatively easy areas with some tough enemies (blink frogs, spiny frogs, hydras, death yaks, catoblepai in lair, liches, aliches in crypt), some tough uniques (Rupert, nessos in lair, Khufu in crypt) that serve to provide some extra exp/loot to players and to allow access to rune(s) in (a) sidebranch(es).

You might call it "the Lair of the midgame," but Crypt is easy by no stretch of the imagination. Not relative to what comes before it, that is. (Vaults are tough...)

Crypt actually is easy, though

Crypt is usually just a fat bag of XP and some loot by the time you get around to it. But if you tried to do crypt instead of lair you would probably find out, to your detriment, that they are not exactly equivalent.

Crypt is shorter too, which is nice.

The main (and only) purpose of Crypt is that it's a place where you get TSO piety.

I sometimes clear it with a necro char who hasn't found yet some good spells I want. Especially with dispel undead at high power is free xp and loot.

Crypt is pretty much a TSO piety storage. And, I guess, a source of some items at the end if you aren't already bored out of your mind by the time you're strong enough to do it.

I always clear Crypt. It's a fun branch (in the past it has been less fun).

crypt is the place where you die to oka wrath