Just had a fun thought, Eagle Wings on Guardian, sure he has a Guard token on him, but after your opponent attacks him once, back into the air he goes.
While that sounds like silly fun and could certainly interrupt an unprepared mage, one could still have a (non-flying) creature attack the guarding Sslak, followed by a QC attack spell (e.g. Hurl Boulder or whatever), which is generally enough to finish off a Sslak and isn't really different than the usual strategy (although with order reversed). And there are other ways to deal with a flying Sslak that an opposing mage might already be packing, like [mwcard=MW1Q14]Lash of Hellfire[/mwcard]/[mwcard=MW1Q18]Mage Staff[/mwcard]/[mwcard=DNQ08]Vinewhip Staff[/mwcard] (not to mention ranged weapons and creatures with ranged attacks). Of course, if you keep the Eagle Wings FD and the mage uses their attack spell first, then you reveal the Eagle Wings when the non-flying creature moves in for its attack, it could delay the V'tar gain (and other bonuses) by a round.
The more I think about it, the more I'm leaning towards including Mage Staff in every Domination spell book (except perhaps Warlords, who might opt for [mwcard=MW1Q13]Ivarium Longbow[/mwcard] instead - until Heart of Gravikor makes an appearance in a legal set), both as a back-up weapon and for its utility dealing with Flying and Incorporeal at such a low sbp and mana cost.
