On the first day, there was a mystery.
On the second day, there was darkness.
On the third day, there were pirates.
On the fourth day, there was war.
On the fifth day, there was fear.
On the sixth day, there was sorcery.
On the seventh day, there was a choice.
~ The Keys to the Kingdom

Seven Morrow Days are the main villains of the Keys to the Kingdom series. They are seven Trustees of the Architect, named after the seven days of the week, are superior Denizens who disobeyed the Will and chose to keep the Keys and their demesnes instead of giving them to the Rightful Heir (for that would cause their own demises).

They broke the Will into seven pieces, then separated and concealed each of the pieces. However they could not entirely resist the Will's destructive influence, so in time each of the Trustee's nature changed and each became afflicted with one of the Seven Deadly Sins. Drowned Wednesday is the only Trustee who, after breaking it, changed her mind and wished to follow the Will, but was stopped by all Trustees, with the exception of Monday. Minus the power given to them by the Architect's Keys, they are ordinary, but extremely strong and resilient Denizens, though they can be killed (the exception being Saturday, who as well as being a key holder, is also a skilled sorcerer).

After their respectively defeat, most of the Trustees are redeemed or quit their crimes except Saturday.

Morrow Day Domain Sin Key Command centre
Mister Monday The Lower House Sloth A sword with resemblance to the hands of a clock, it can be split into two separate keys, the Lesser (minute hand) and the Greater (hour hand). Monday's Dayroom
Grim Tuesday The Far Reaches Greed A pair of shining gauntlets, transformed into gloves by Dame Primus when she is wearing them Tuesday's Pyramid
Drowned Wednesday The Border Sea Gluttony A fork-like trident (changes size depending on danger or user's mood) Wednesday's Lookout, now Port Wednesday (Originally Wednesday's Lighthouse before Wednesday's transformation into a Leviathan)
Sir Thursday The Great Maze Wrath A military baton (when danger is present, it manifests as a broadsword for Sir Thursday, and a rapier for Arthur) Thursday's Citadel
Lady Friday The Middle House Lust A silver mirror Friday's Scriptorium
Superior Saturday The Upper House Envy A Peacock quill pen Saturday's Tower
Lord Sunday The Incomparable Gardens Pride A very small golden key Sunday's Elysium