Shadow creep is an interesting archetype, but shadow creep in itself has its own kind of archetypes, and there are some rarely used shadow creep cards due to the fact that these two uses work differently. There are resource and positonal based shadow creep.
Resource based creep
This is the shadow creep style that you see now. Basically, these types of cards depend on the number of creep you have, it doesn’t matter where it is, just the simple fact that you have it, you can just vomit creep on the board and get value wherever it is.
Cards that fall under this category:
And of course obliterate
Positional based creep
These types of cards are basically the opposite of resource based, which is the reason they are rarely used. Cards that depend on where your creep is, rather than how much you have. You want your creep to spawn in certain places rather then spawning as much as you can wherever possible.
These cards include:
And the most important card for this type, shadow nova.
Now I have some ideas for how positional based creep could become more viable.
Maybe you could have a cheap but powerful flying minion, that reads “if this minion is not standing on shadow creep, destroy it”
Perhaps a spell that would spawn a wraithling on all shadow creep tiles in 3x3 area (or some similar restricted summoning effect)
More cards like night fiend obviously.
Some type of effect that buffs friendly minions standing on shadow creep.
Some kind of card that effects a targeted shadow creep tile, then removes said tile.