UPDATE: i assume the original person who wrote up this crag meant the large meltwater canyon when they say 'crevase' below. judging by most of the photos that is where most people have been climbing.
Crevasses on the right bank of the Mer de Glace approx 300m South (up stream) of the point where Vire des Guides Echelles ascends the lateral morraine. A good spot to play when strong Southerly winds would otherwise keep you in the valley.
Plenty of opportunities for ice climbing on the slab and wall at the lake as well as on most of the crevass'.
There is also a glacial moulon which may be explored if it can be found. (currently (2020) this can be found approximately level with the large yellow square painted on the cliffs marking the start of the Charpoua refuge approach path, but of course it is moving down stream!)
Only 20 minutes walk up the glacier from the bottom of the ladders at Montenvers.
Train from Chamonix to Montenvers then fixed ladders down rock faces to the glacier, head off SE up the glacier aiming for the far (right bank). In good visibility you can see the ice cliffs. You are unlikely to be alone as it is a popular spot for guides to take novice ice climbers. The best spot for steep ice in the canyon is currently (2020) approximately level with the start of the new ladders to the Envers refuge, though of course this is changing every year)