Hello there, ive been trying to make a very similar version of this deck for Legacy, and besides that the formats are quite different, Ill like to share thoughts
1 First the Mongrel is great!!! fine beater even in Legacy with a very huge creature base, the mongrel rocks!
2 krovikan Horror might help to increase the rate of zombies.
3 Circular logic
4 Ive been trying diabolic intent, but seems win more
5 Could this engine be transformed into a contamination/stax deck?
6 At least for extended Enigma and verdant Eidolons, plus Cavern harpy were awesome but too inconsistant, maybe survival of the fittest, will help, but im just guessing.

I hear you comments.

Hi, The only good creature I can come out with is Sliver Queen, i dont really know why you should be placng tha card in your deck, but is an idea, and you can get lots of sliver tokens, good for stax I guess, but is extremely marginal and should get a lot of tunning to get all the juice out of it.
Otherwise, Ill try to recomend you to squeese all the marginal and narrow/one use creatures to instead focus the toolbox to absolutely need to perform the combo as fast and resiliant as you can be, let the rest for the Sideboard where it belongs.

Hello Everyone, My name Is Alejandro Im from Argentina.

Over here in the southern emisphere things are not very good for a magic player. Cards are three to four times more expensive than in the States, because of the country´s Economic´s policys and the dealers guile.
Im mostly a Legacy player, though casual mainly (there are actually no place to play lecagy on a regular basis) I started playing by the time of fifth edition, dropped after seing that sixth edition was lousy, and returned by the times that Mirrodin proved that from time to time, Wizards prints some power.