Tuesday's Yan is Grim Tuesdays strongest servant. It is the highest in predence of the Grotesque's. The Grotesques were formerly his Dawn, Noon and Dusk, before he used the Second Key and copious amounts of Nothing to merge them into Seven beings.
Under Grim Tuesday
They were lesser beings than the other Morrow Days servants and had breath that can erase memory and kill, they also have poision spurs in their thumbs.
The Grotesque's appearence are of slightly short Superior Denizens, they each have broken-looking nose seperating sunken eyes. Their eyes are blue and green. They generally wear aprons. They always carry tools with them, along with Silver rings for Scouchers and also Crystal swords to kill any other Nithlings.
Yan was killed just after Arthur fixed the Southern Butress, and before Arthur managed to rectify Tuesday's mistake with his Dawn, Noon and Dusk and Saturday's Dusk stabbed Yan, Killing all the Grotesques.
Under Lord Arthur
It is possible that Mathias, the supply clerk, became Tuesday's Dawn and Tuesday's Dusk Japeth. Although it is also likely that Monday's Dawn, Noon and Dusk we're also appointed Tuesdays Dawn, Noon and Dusk.