I did the route a long time ago. It was probably in spring conditions--IIRC the snow was consolidated. We carried, but did not use a rope or any protection. It is steep enough that self-arrest would be difficult. There was evidence of past avalanches all around, including the Gully itself.
The main line of the gully goes over a cliff near the bottom. (The climbing route goes around it on the right.) If you fall from above it, you will most likely go over it...
Around 1980, two climbers were avalanched off the route and over the cliff. They survived, but their injuries were severe enough that they were unable to self-evacuate. They were lucky enough to attract the attention of a hiker who went out for help. (This may the the accident that Mohamed described.)
Recently (past year or two), an experienced climber fell (unroped) from high in the gully and died. He was last in the party and no one saw him fall so the details are unknown.
The climb itself is a snow climb--I don't recall any opportunities for ice protection. (The cliff ices up, but you don't go over it.) You might be able to get a rock placement in the sidewall, but I again don't recall any details. I'd expect only snow protection although it might not hurt to carry a few light-weight rock pieces.
I don't think I would go in there in December--the snow is likely to be unconsolidated and avalanche prone. I'd wait until early Spring. The area is completely unpatrolled so you are on your own with respect to evaluating conditions or rescue. The Gully is north-facing, similar the headwall of the Great Gulf. The Great Gulf headwall is a (somewhat) popular ski route, so you might monitor skiing websites to guesstimate conditions on Great Gully. It would also be worth knowing something about avalanche risk prediction.
Approaching the base of the Gully in December may also be difficult--too much soft snow and the trail is unlikely to be broken out.
Doug