Daily Card Redesign is a daily Magic: The Gathering design exercise where I randomly choose a card for the scenario of it being scrapped late during its own set's development. I design a replacement card that uses the same art, is the same color(s), is the same rarity, and has a name that, alphabetically, keeps it within the same collector number for the set. This real-life Magic R&D process is known as "hole-filling."
The focus is on the object being held. This feels like the caster of this card isn't really taking action but moreso of reacting, being passive. Thus, hitting attacking creatures. Also, cumulative upkeep, which was a mechanic in Ice Age, is one that promotes being passive, biding your time.
I like that the longer the opponent waits to attack, the worse consequence it will be. Thus, the opponent will keep attacking. And having the opponent just sit and wait out the scepter means you were able to stall out being damaged for a while.
Since the opponent is going to prolly keep attacking you, there's a tension in decision-making ...do you affect a creature now or wait for a better target/chance later?
Lastly, this place depicts somewhere underground. This is why the effect was chosen of putting a creature underneath cards on top of the library, since that gives the feeling of "casting a creature downward into the earth". Eventually, they'll resurface. :)
The alphabetical ordering of this set looked like this:
So, Subterranean was chosen as the word that comes before Sunstone but still refers to the setting depicted in the art (and the type of magic being cast). Scepter was chosen just to shake it up from "Staff."
For similar effects for costing purposes, I looked to blue and saw that it costs three mana to put a creature on top of its owner's library. Since this is an artifact that costs generic, I needed to turn one of those blue mana symbols into two generic mana cost. Thus, the 4 mana casting cost.
Oddly, both of these similar cards are also similarly-named. Perhaps future cards can just do "_____ Away". Though, sometimes, this means bouncing something to someone's hand instead of library, like Wipe Away.