A fun card that acts as a way to deal with intercept and reduce the threat from a powerful creature. It's cheap but you pay for the versatility with it only lasting two turns.
What I like most about Shrink is the flavor. The idea of what the card does can be clearly represented by the mechanical benefits.
Also, just like the hydra is an abomination created by wizards toying with nature, I like to think that all house cats in Etheria are just products of a bored wizard who decided to make a quick buck and sell adorable kittens.
On the one hand, I love this card for lots of reasons: flavour, temporary effect, mana cost that scales with how powerful the target is, etc. It's like a temporary Arcane [mwcard=MW1E09]Agony[/mwcard] that might be cheaper to cast, especially on low level creatures that have been buffed up (e.g. Charging [mwcard=MW1C14]Feral Bobcat[/mwcard] with [mwcard=MW1E01]Bear Strength[/mwcard] or something). And it works against Attack Spells (!) and messes with Guards, too - so it's quite a bit better and more versatile than Agony in many situations. Could be used on a Thoughtspore or Sersiryx to (partially) negate their Attack Spells, or could be used on Cerberus or a Sslak...
On the other hand, as the first spoiler from Academy, I'm a little concerned. The Academy product is designed to be a simpler, quicker, more portable and more streamlined intro into the Mage Wars universe (in comparison to Arena), and as such supposedly uses fewer key words and simpler mechanics (e.g. I was thinking no more than 2 keywords on a card, straightforward card interactions, etc). This spoiler is an Enchantment with an effect similar to putting 2 Weak condition tokens (which, as an aside, are definitely in Academy as per other spoilers that are around, e.g. the promo cards that come with Academy pre-orders) on the target that go away over time... but uses the Dissipate keyword... so instead of putting 2 Weak tokens on the target and having, say, 1 token removed each round during Upkeep, you remove Dissipate tokens and when they're gone you destroy the Enchantment. This works fine mechanically, but Dissipate is one of the rarer mechanics in Mage Wars and not as straightforward as some. OK, I concede that Dissipate isn't that hard to grasp, it's a little gamey. Also, consider putting Shrink on a creature, then hitting it with some attacks that deal out Weak tokens (from Gorgon Spearthrowers?)... so kind of doing a double-whammy, then the Shrink goes away but the Weak tokens don't.
If this were the 5th or 6th spoiler after seeing some simpler cards, I'd feel more secure that Arcane Wonders is going to get the results they want with this set. Of course, maybe simple cards wouldn't make for good previews because they're kind of boring, so they showed us something a little flashier (?).