The names I can read are: Emma, Rumple, Zoso, and Gorgon (which I suppose is the creature that Head!Rumpel turned into in episode 1 of the season. Who knew animals could be dark ones?) and there is also something along the lines of Dragonkiu or something.
I guess it is counting backwards to the first dark one.
EDIT: I was right. Gorgon the invincible is what Head!Rumpel turned into in the first episode. His name appears on the dagger
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"I could have the giant duck as my steed!" --Daniel Radcliffe
Keeper Of Tamara's Taser , Jafar's Staff, Kitsis’s Glasses , Ariel’s Tail, Dopey's Hat , Peter Pan’s Shadow, Outfit, & Pied Cloak,Red Queen's Castle, White Rabbit's Power To World Hop, Zelena's BroomStick, & ALL MAGIC