Shenanigans: that restaurant with all the goofy shit on the walls
Here's the theory: jam pack a build that uses weenie synergy and plays around with critters living and dying, then out flood opponent with quick material that doesn't stop accumulating. I've made a few of these before, but running the idea with Phelia in the mix makes it even more potent.
The build does what all weenie decks wants to do, out speed opponent and out material opponent's spot removal. To accomplish this, we've maxed out the critter count, bypassing the dead topdecked lands in the process. Your Hierarchs, Zeniths, and double-sided lands means the build is effectively running 28 lands, but in actuality you're only running 14. What's more, when you don't need the Hierarchs anymore, they have double functions, in that they either pump your attackers, act as fodder for Chthonian Nightmare, are great targets for Soul Cauldron, or as murder fodder for Grist. Zenith puts itself back in the deck and only gets better with more mana, so your deck stays in a good ratio to topdeck material, especially with fetch lands tweaking the math (which is usual but worth noting as Zenith does the same thing so they stack). Long story short, the math is on your side to topdeck something impactful every turn.
The other focus of the build is stacking synergy through recursion, toolbox, and bullshit material quirks. Chthonian Nightmare lets you reuse your ETB effects, which is particularly useful, and this same model is doubly effective because Phelia effectively does the same thing. You can pretty consistently mill yourself, hate on opponent's grave, spot removal artifacts and enchantments, make tokens, and recur weenies. You've also got all the perks of the Phelia machine, such as cheating in Overlord, resetting Grist, banking energy with Nightmare so you can recur Overlord, etc.
You've also got your critter fodder you wouldn't mind sacking to Nightmare, Young Wolf and Stitcher's Supplier, both of which benefit you through the sac. Then there's all the cheese you can conjure with the Zenith, Grist, Soul Cauldron love triangle, all of which fits in perfectly with Nightmare and the extra mana and material the build is trying to conjure. The Zenith shenanigans alone make this build interesting, as you're effectively running +4 of most of what you actually want with an extra +4 outs at all times because of the utility. Math can be fun sometimes.
Overall, you'll hopefully have the edge in both tempo and material and can outdo opponent in at least one or the other. So, when opponent can spot removal your first few turns, you'll have more coming, and when opponent can't, you've got him on a clock that's ticking faster than he'd like.
Thoughts appreciated.