HOW TO PLAY THIS JANK

1. Ideal hands have 1 Reliquary Tower and Treasure Hunt. You can mulligan down pretty far to at least get a Treasure Hunt.

2. Cast Treasure Hunt until you get to a Zombie Infestation . Discard 12-20 lands. Swing Zombies to victory.

Reliquary Tower is important to avoiding board wipes. It lets you drop your massive horde at the end of your opponent's turn, and then you win.

Discussion

First off, this is probably the most hilarious deck I've ever played. While one of the downsides of Magic Online is that you can't actually see your opponents face, I have to imagine there are some good ones. While our opponents are playing "good cards," we are trying to draw 37 cards for two mana with Treasure Hunt and than win with a horde of zombie tokens from Zombie Infestation.

We also get to play the fun mini-game every time we draw our opening hand. Since the first rule of Zombie Hunt is that you can't keep a hand without Treasure Hunt, we literally have to mulligan to one to find it. Thankfully the odds are heavily in favor of us hitting one eventually — the odds are ~86.5%, which means we should only whiff one out of every 7-7.5 games. 

Once we mulligan into our Treasure Hunt, we play another mini-game called "does our opponent have a Thoughtseize or a counterspell" which heightens the drama of the entire situation. Assuming we actually get to cast and resolve Treasure Hunt, we are usually golden and proceed to trample over our opponent in a turn or two. 

Other Notes

The only way I can think of improving the deck is by adding more powerful lands, although I'm really not sure what these might be. I tested Creeping Tar Pit and found that manlands are rarely relevant (although playing five-color Zombie Hunt with 40+ manlands might be an interesting). 

The sideboard might as well be blank. I tried bringing in Duress and Dispel to combat counterspells but found that they weaken our Treasure Hunts too much. The only way for the deck to work is for every Treasure Hunt to hit another Treasure Hunt or a Zombie Infestation. Sideboarding any non-lands spells ruins this plan. 

Boseiju, Who Shelters All might be a good way to fight through counterspells. Since we have so many free land slots, there's little reason not to give it a shot. 

Don't cast Treasure Hunt on turn two unless you have a Reliquary Tower or you'll end up discarding your hand. However, casting it on turn three and hoping to hit a Reliquary Tower is perfectly acceptable. 

Beware of Ghost Quarter hitting your Reliquary Tower. If your opponent is leaving it up, wait another turn before casting your Treasure Hunt so you can play either a second copy of Reliquary Tower or a Zombie Infestation. 

There is another build of this deck that uses Seismic Assault as the win condition rather than Zombie Infestation. While I'm not sure which is better (Seismic Assult kills faster and doesn't require creatures, but Zombie Infestation is much easier to cast), Zombie Infestation is definitely the more budget-friendly version since casting the triple-red Seismic Assult requires a decent amount of dual lands. 

Conclusion

Honestly, I wouldn't recommend Zombie Hunt as your primary Modern deck; it's just too inconsistent. However I highly recommend building it and adding it to your Modern rotation. It is so inexpensive that you really need to try it out at least once, and I would certainly take it to an FNM level event or play it on the kitchen table.