The ominous, deep cleft high and left on Thatchtop, above the Loch. Usually best approached from the right after climbing Necrophelia (though other ways, including a sometimes formed direct chimney, can be had), making for a great day of hard ice and mixed. From the shelf atop Necro, the climbing is easy and rambling to reach the crux final pillar, which is most often climbed as a steep ice pitch. However, when the pillar isn't touching, there can be brilliant mixed climbing - fairly hard, and all free-hangers are serious (and pumpy!), of course. These conditions are normally found early season, so be ready! A great route.
Protection
If it's all ice, it can protect with all ice screws. However, excellent cracks border the bottom half of the left-hand side of the crux final pillar - assorted nuts, and finger to hand-sized cams to form a medium rock rack are good. There's a fixed anchor at the top and in the gully all the way down (unless you walk-off left), but be prepared to leave your own if you can't find them or they're gone.
Last Wed, Oct 17, Scott DeCapio and I climbed this route after Necrophelia - sorry I slacked in reporting sooner. Was far better than Necro, offering superb mixed climbing. The final pillar wasn't anywhere close to touching, but great rock climbing (felt 5.9-ish - good pick locks & hand jams) with good pro led to it. Unfortunately, the cracks ended, so the awkward and strenuous climbing onto the upper dagger were run-out (unless you want to place screws in it to experiment with natural selection). Water was running off the pillar, it was chilly, and it's colder now - it may be getting fatter.
Deep Freeze in good shape, climbed it a few weeks ago. The first pitch is WI3 with good rock gear. The 2nd pitch is 30 feet of dry tooling (M5) to a exciting yet awkward chimney. Mostly good gear the whole way. On the way down my ice tool managed to work loose out of my harness and [disappear]. It is a Cork hammer with a new pick, reward if found.
When the (start) chimney pitch of Deep Freeze is being a nasty bugger, and the tunnel is choked with endless sugar; the first WI3 pitch of North Gully on Thatchtop makes a great way to access Deep Freeze. The broad terrace safely traverses to the right and is an easy walk when dry. Even with snow, it was easy to simlu. climb. It will deliver you in the gully below the WI4 pitch of Deep Freeze. Enjoy.