Artist Eric Deschamps has illustrated 47 Magic cards. They're good!
The first step of the creation of a card's art is its art description. The art description tells the artist what the card will do, what its flavor is, and what the mood of the illustration should be. Here's what Eric was given for the card:
Color: Black Creature
Location: Abandoned, decrepit manor house.
Action: Show a skeleton creeping down the grand staircase in an abandoned, decrepit manor houses. He's holding a burning candle in a silver candleholder. He's wearing rotted clothing that hangs loosely off his bones.
Focus: The skeleton
Mood: The dead manservant who will never leave his master's house.
Here's the first sketch that Eric gave to the creative team:
That looks good, but the creative team thought it could be creepier. They asked Eric to take another shot at it.
Ah! Much more skeleton-y! Skeletonic? Fine, "skeletal." If you must.
Here's the final card as it will appear in Innistrad booster packs: