Dread Return has flashback, not buyback, thus it is exiled after it is cast from the yard.
-Second Wind has 'Enchant creature. T: Tap enchanted creature. T: Untap enchanted creature.'
>In case there's confusion at this point, from gatherer: These abilities are abilities of the Aura, not abilities granted to the creature. Only the Aura’s controller can activate them.
Quote from lyonhaert »Magnivore's point is that you tap Second Wind in order to untap Macar. There isn't anything untapping Second Wind to be able to repeat this, so no, that's not much of a combo.
Quote from TEREBUD »Exile all creature you want on battlefield.
King Macar, the Gold-Cursed + Second Wind
Quote from Magnivore »Uhm, no. Those abilities are the aura's abilities, not the creatures.
Haven't tried Opal Palace in this deck. It's a decent enough card but I don't like to run too many colorless lands. The only reason is for Dakkon but he'll be big already when he comes out and unless you are going from 10 to 11 power, a minor boost like that doesn't matter much. By himself he still needs to connect twice. YMMV though.