So, that's all kind of exciting. Thank you, James, for tracking this down!
Here we have a Mammoth Mummy. Let's assume that this mummy is roughly the size of a hill giant and stat it up from there!
Mammoth Mummy : Init -1; Atk fist +8 melee
(1d8+8) or choke +8 melee (1d6/2d6/3d6/etc.) or hurled object +6 ranged (1d8+6, range 100’);
AC 14; HD 14d12+14; hp 99; MV 30’; Act 1d24; SP un-dead, infravision, crit on 20-24, damage reduction 7, vulnerable to fire; SV Fort +12, Ref +5, Will +16; AL C.
Most mummies are ponderous and slow, but the Mammoth Mummy is not. It stands at 12’ tall and weights 700 lbs., its shriveled flesh being lighter than that of a living creature of its size. Unlike normal mummies, the Mammoth Mummy does not carry the dreaded mummy rot.
Indeed, left on its own, it will merely haunt the city streets at night, returning to its museum home during the day.
(In a DCC game, this will be a private museum, but in an MCC game, it may be a museum of the Ancients, and the city the Mammoth Mummy haunts may be no more than a ruin.)
The other special abilities are very much like those of standard mummies, save they are written on a larger scale! The Mammoth Mummy has been known to stop at taverns during its nightly haunts, and although it has no money, it is peaceful enough if served. It's name is Ptahhotep, and it knows many things about the world as it once was (in ancient or Ancient times, depending upon the game).
The Mammoth Mummy can be used as a quest giver, a source of information that the PCs can use to Quest For It, a curiosity, an opponent, or even a rescuer coming out of the dark night and the fog. Visited in the museum, Ptahhotep is unmoving unless threatened or attacked.