For my money, the theme is life totals and cards that interact with them. Think Pulse of the Forge, Pulse of the Fields, Convalescent Care, Hidetsugu's Second Rite, and many many more. It fits perfectly with mana burn going away in M10 -- after all, they've always said there was a lot of design space that mana burn prevented them from using effectively. Now they can!
Or maybe (much more balanced) you remove it from the game. There's a lot of "remove" and "game".
I was going to point this out, but you beat me to it (my internet was down for a while). The number of "remove" and "game" lines up VERY nicely with the number of "unearth."
I will *speculate* that unearth reads as follows:
"Unearth [cost]: Return ~this~ from your graveyard to play. ~This~ has haste. At the end of the turn, remove it from the game. Play this ability only as a sorcery."
Plus I expect one or two cards to have abilities like "When ~this~ comes into play, if you paid its unearth cost, ..." or "Whenever you unearth a creature, ..."
Though of course spoilers are always nice, I hardly find either of these cards exciting. The Gwyllion is fine for limited, but 2/4 for 4 is nothing special, Wither or no. The Troll regenerates for two mana, which is one too much, so I don't even see it being a good limited pick, especially in -1/-1 counter world. And no, it's nothing all that unique...
"Q: Used to represent something new coming in Jelly. Chosen by its creator (Mark Gottlieb) because the letter that would have been most obvious was already used." -- from The X Files
I'm sure someone already observed this, but I don't see it in the thread, so I'll point out the obvious: Untap strongly fits this point, given the use of U for blue mana.
I have to say, I have played a lot of Kamigawa Block, and though it is only one set so far, I have to say that splice in various forms (G/B with Hana Kami/Soulless Revival, R/x with Glacial Ray, maybe even U/W Dampen Thought, and so on) is a definite block competitor and such decks won't be happy to get their stuff countered by this card. Especially if there end up being alternate (non-mana) splice cost spells, splice could be important and this counter could be a strong sideboard card at least in block (competing with Hisoka's Defiance, I would assume).
Gatherer lists:
Boggart Arsonists, Graceful Antelope, Zodiac Rooster, Righteous Avengers
4, making this 6/5.
EDIT: Oops I see the OP says it's meant to be 4.
I was going to point this out, but you beat me to it (my internet was down for a while). The number of "remove" and "game" lines up VERY nicely with the number of "unearth."
I will *speculate* that unearth reads as follows:
"Unearth [cost]: Return ~this~ from your graveyard to play. ~This~ has haste. At the end of the turn, remove it from the game. Play this ability only as a sorcery."
Plus I expect one or two cards to have abilities like "When ~this~ comes into play, if you paid its unearth cost, ..." or "Whenever you unearth a creature, ..."
Urborg Skeleton, Will-o'-the-Wisp, Votary of the Conclave, Rimebound Dead, Soldevi Sentry, Village Elder, and technially even Clergy of the Holy Nimbus and Kjeldoran Dead would all like a word with you.
I'm sure someone already observed this, but I don't see it in the thread, so I'll point out the obvious: Untap strongly fits this point, given the use of U for blue mana.