I think that some way to scry will help for the combo...

We're in Green here, what would you like to offer that is Green that scrys?

It is not green but Seer's Lantern scrys anyway.

True, but what do you think could be cut for it?

I don't know... some lands and some sylvan scrying? I don't really know

A more out of the box idea might be to replace the 4 Sylvan Scrying and 8 Forests with 4 Pulse of Murasa and 4 Windswept Heath and 4 Wooded Foothills. The quality of your land fetching suffers a bit but you improve your defenses with some incidental lifegain and recovery from opposing spot removal, plus some slight improvement to card draw quality. It does remove the turn-2-scrying-turn-3-From Beyond or Eyeless Watcher scenario though. Maybe that also hurts your ramp curve too much too.

Kanokarob, you could try llanowar empath, that would also allow you to dig for a deceiver of form...

That is true but the problem is still what to cut for it.

After play testing this deck, I found that it was really easy to simply chunk block your creatures and not take any damage. Eventually, your deck will be grinded away if you can't find any other way to remove your opponents creatures. To keep with your colorless theme I suggest Breaker of Armies. This will force your opponents to block that creature and also will work well with Conduit of Ruin and Deceiver of Form.

Are you not turning your Scions into Bane of Bala Ged? They should be exiling most if not all of their permanents, creatures included... There's no need to make them block a breaker of Armies when they have nothing to block with anyway.

If you face an opponent that can produce scions (or any type of token for that matter) You may find people will have plenty of things to block with. Then simply fly over you. Just saying this is what happened when I play- tested your deck. You'll need some sort of a board-wipe. Breaker of Armies could help you. Bane of Bala Ged doesn't allow you to choose what gets exiled. By the time Bane of Bala Ged gets out, they'll likely exile land before going to creatures. This deck has no defense for flying.

I can see the block-then-fly-over-you scenario. You can probably stuff that with a World Breaker or two in the sideboard.

But I like what @kanokarob is doing here. I tried taking his shell and swapping out the scion-based package for an Eldrazi Displacer + manifest package featuring fun stuff like Whisperwood Elemental, Wildcall and Mastery of the Unseen. For mana ramping I'm relying more on just Pulse of Murasa, Honored Hierarch and From Beyond which is not as good but does put in work. But being able to cheat some of the big guys into play via just a Displacer blink helps discount the costs too.

I'm enjoying the manifest version a lot more. All the manifests kinda give you the same kind of benefits that a bunch of scrys would. You get good lifegain from the Pulse and Mastery.

But I had to look up the rulings on Deceiver of Form vs manifest. When a face down manifest creature becomes a copy of something else, it's still a face down manifest copy of that creature. The opponent may not know what it was originally, but he'll know what it is while it's copying.

Brood Birthing is dead weight. None of your other cards generate spawn (they generate scions), so you can't meet the spotting requirement to activate it.

Ah yes, I forgot I had taken out Kozilek's Predator early on in the reformatting. I think then From Beyond would be more useful. Search power and singular Scion generation over multiple turns.

It That Betrays instead of the pathrazer

Have you also considered cuting Brood Monitor for Elvish Mystic or other mana dorks

If you are worried about lacking colorless mana Boreal Druid will do good

It That Betrays is much more cruel, but Pathrazer of Ulamog is a better target for two reasons.

A: Pathrazer has Annihilator 3, so the copies will hit more things total, leaving less possibility of them having just enough resources to do something the rest of the game.

B: Pathrazer has triple menace, keeping the opponent from just saccing off their lands, chump blocking, and killing me on the backswing with tokens or whatever.

It that betrays is better if I expect the game to go longer. Pathrazer is better because it makes the game not have to go longer.

As for mana dorks, yes I did consider them, but as the creature-mana is only slightly relevant and therefore Cryptolith Rite is fine enough, and as I'm playing Eldrazi Temples anyway and Brood Monitor is 4 creatures for 6 mana, but only takes up four deck slots, it seemed like the better option to me.

Have you thought about a card to put Pathrazer on the top of your deck deliberately?

For a budget, maybe splashing blue would do it, with Riverwise Augur?

The best bet though might be Cream of the Crop.

Alternatively, Brutalizer Exarch, Silhana Wayfinder, or Primal Command can all do it.

I tried playing with it a bit, and you need some pretty particular conditions to set up for it to combo out. Making that a little easier and quicker, at least against other aggro decks, makes sense to me.

Yeah. I'm convinced. Cream of the Crop should replace:

1 Brood Monitor 2 Second Harvest 1 Planar Bridge

I'm also going to suggest getting a fourth Pathrazer.

Put the bridge in the sideboard, but ditch the Brood Monitor (I might ditch all three).

This is really interesting. Building a viable sideboard to handle common threats is the next step.

Keep it up, this is a cool brew.

Last thought-- I hadn't realized how effective the Conduit of Ruin was for getting Pathrazer.

A splash of Black might make you a lot more flexible-- Catacomb Sifter has a lot of value for you.

Skittering Invasion might have a home here...

Skittering Invasion was included at one point, but was found to not do enough often enough. Even just 3 tokens can win a game, but you gotta have Deceiver and Conduit, so more effort was put into finding those.

Maybe include Tomb of the Spirit Dragon as a one of? Not a bad card if you have a bunch of Scions on board and the mana to spend.