card at a time, courtesy of Gatherer's "Random Card" button.
Myr Battlesphere (Scars of Mirrodin, 2010)
Scars of Mirrodin was the sequel to one of Magic's all-time most popular and best-selling blocks, 2003's Mirrodin. This set marked, I believe, Magic's first true sequel, in terms of being a return to a previous, popular setting years afterwards, as opposed to simply continuing a single story from one set or block into another. (You could make an argument that Unhinged was a sequel to Unglued, but that's not quite the same thing.) Mirrodin sold very well but also created a great deal of problems. There were a number of cards and mechanics in the set that were simply too powerful, and the prevalence of degenerate combo decks created serious imbalances. Historically, whenever the game has been dominated by specific powerful cards and strategies for any amount of time, tournament attendance has plummeted - few players relish seeing endless identical mirror-matches between the same decks competing to get turn-one kills. If anything, Scars of Mirrodin compensated by being underpowered, and reception among long-term fans was mixed.
In case you are completely unfamiliar with Magic lore (and really, why would you be?), Mirrodin was (past tense, since it's since been conquered) an artificial all-metal world created by the artifact Planeswalker Karn after the storyline in the Odyssey block. (In Magic, "planes" are the different worlds that make up the game's multiverse setting.) Creating an artificial plane was a big deal, and it hurt Karn significantly to do so. This is important, because the premise of the Scars block was that partly due to Karn's weakness the plane had been infected by the evil Phyrexians. (It's slightly more complicated than that, of course: the creation of Mirrodin is the end of a long chain of events going right back to the "Brothers' War" between Mishra and Urza which was the main event in Magic history all the way back to the Alpha in 1993. The Phyrexians are Magic's marquee baddies, less a race than an infection that spreads indiscriminately across the multiverse in the form of a viscous black goo that transforms its victims into monsters, kind of like the Borg crossed with the Thing [1982 version, naturally].)
One of the things I like about Magic is the hard work they put into building credible and original fantasy settings. They've gone on record as saying that the contemporary version of the game consciously works to avoid things like your stereotypical bearded wizards with pointy hats. This is done at least partly to differentiate the game from Wizards' other famous fantasy property, Dungeons & Dragons, which has always trafficked more heavily in the iconography of traditional epic fantasy. It's a fine line that doesn't actually signify much in practice - the game is still filled with wizards and dragons, after all, but in practical terms it means that Magic is far more likely to play around with less-traditional fantasy stuff like steampunk, splatterpunk, H.P. Lovecraft, Japanese myth, and now with 2013's Theros block, Greek myth. Mirrodin and its sequel are (so far) the furthest the game has gone into the realms of science-fiction - which means, in the case of our Myr friends, cute little robots who can gang up en masse to present a surprising threat.
Scars of Mirrodin was a fun set, playwise. The problem I had with it was that, story-wise, it was really depressing. The Phyrexians won: even though Karn was reborn and once again became an extremely powerful Planeswalker, Mirrodin was conquered by an army of Clive Barker monsters, and that meant that all those cute little Myrs were either corrupted or literally hounded to extinction. That last link there is seriously upsetting: the cute little robots literally on the run for their lives from an army of fiends. That's sad! Why would you want to play the killing-robot-teddy-bears game?
But it must be said, Myr Battlesphere is a good card. If this thing resolves and is able to attack, and you do not have any removal, chances are good that you will lose the game. Myr decks have a lot of ways to get big artifact creatures on the table prematurely - I think I've seen this guy as early as turn three. It's not very fun to be on the receiving end when this fellow goes rolling down the hill.