My best advice would be obtain the Shock lands at least 3 of each and 3 of each other dual lands cut the guildgates and you will be fine. Also I would run Farseek over your Caravan Vigil since it will allow you the chance to dig your shocklands out and balance your deck a little bit better. The Stability that shock lands provide are a must imo!

Other than that I like the deck seems pretty legit and effective. +1 from me!

I would either drop Demonlord of Ashmouth or card:Altar's Reap.

Demonlord of Ashmouth is a HELL of a scary attacker but that sacrifice clause could wind up biting you in the ass if someone picks off your only sacrifice bait.

card:Altar's Reap is a really good form of draw but keep in mind, you're playing aggro/midrange here, a little draw is nice but you don't want to over do it. You want to be playing threats with that 2 mana not sacing to draw. Also, you have Zameck Guildmage who will be not only resetting your undying but drawing you cards. Yes it's not good to rely on one thing but you don't really need the draw.

Imagine yourself in a locked board with no creatures and you topdeck either of these. Which would you rather have? In mine (which you've looked at) I don't have anything that I'm sad to topdeck aside from Simic Charm .

I'd have to agree with Ohthenoises. Drop the card:Altar's Reap, but I personally think that the Demonlord of Ashmouth hits too hard to drop. Plus it's perfect synergy imo...

Consider adding Gyre Sage , Shambleshark , or just bumping up to playsets of Dimir Charm , Syncopate , and Caravan Vigil .

have you considered Gutter Grime kill off an undying creature it comes back you get an ooze token, maybe a creature or two get a +1/+1 counter remove the counter repeat Tell each ooze powers up your creatures.

How has Fathom Mage been working for you? I got her in my pre-release and I've tested with her before and found that she is a huge letdown most times. 4 mana is just a lot for an aggro deck to invest for a 1/1 even with Evolve.

Gyre Sage could help you ramp into your 5 drops while making a fairly decent beater in the endgame.

I think this deck would be great with more black in it, somehow work in Mikaeus, the Unhallowed because then all your creatures have Undying! and I agree with @Othenoises i never liked the idea of fathom mage because she's 4 mana when you can get far better cards for 4 mana like Unexpected Results

Ohthenoises, she's definitely been kind of "meh." I like her because she can almost consistently draw me cards, but when I can get Vorapede for one more mana, it usually hurts to play her. So far I haven't been able to get Gyre Sage to work for me most of the time, either... but a "meh" 2-drop is definitely better than a "meh" 4-drop, haha.

Royberto, I initially did have black in this deck, but I took it out because I was stretching my colors so far, which especially works when i specifically need GU to use Zameck's effect. Even if I did keep black, I definitely wouldn't use Mikaeus, the Unhallowed . The BBB in his cost would be very hard to pull off. And besides, Most of the stuff in this deck already has undying. If I was to run something with BBB, it would be card:Geralf's Messenger.

Wow, my brain went crazy when I was typing that. I meant to type "which especially sucks", not "works". Doh.

I wouldn't always call Gyre Sage meh. I've seen her get to Goyf-like proportions in the 2 turns it takes for her to push out a Vorapede and once he is out I've seen her get to be a 6/7. (4/5 before casting Vorapede 5/6 for casting him and 6/7 on the undying re-entry, granted you should have won by then but still.)

Also, a larger butt makes her an ideal blocker for turns where you think you may need the mana.

I'm also doing some testing with Wolfir Avenger and so far I am not disappointed. A 3/3 for 3 with Flash and 1G: Regenerate is pretty damn good and can make a great backup plan should someone pick off your Zameck Guildmage . (Also, he Evolves your Cloudfin Raptor into a 3/4 without needing the Strangleroot Geist to die.

Any heavy Simic deck needs Bioshift . It would be added insurance you wouldn't lose a creature after Undying took effect on it, or to buff your Wolfir Avenger after it's been on the battlefield after a while, letting your other creatures evolve again.