silvertuerk

https://www.moxfield.com/decks/M0Xq-KLoqEOGkC5NuKn8XA

1. 1x Cloak and Dagger for resilience and fun?
2. Dauthi Voidwalker seems anti-synergic late game mini-bomb at first glance.
3. Difficult to assess but if +1/+1 counters are of major importance - 1x Nesting Grounds
4. Thought Scour if and only if milling is not fast enough

if you like to review yourself,
My recreational ninja deck with some rogues: https://www.mtgvault.com/silvertuerk/decks/ninja-2024/

Oona's Blackguard in the early game is very nice, Thieves' Guild Enforcer is great lethal surprise.

Death Baron or something like that would be nice tribal boost.
Headless Rider would be protection for board swipes.

Cathedral of War?
Arena?
Lotus Cobra?

Gravecrawled is very strong card. Black Cat I like, it has cool mechanic -- it would synergize with zombies or vampires that cause target player, each opponent or each player to discard a card.

Modern legal colorless lands that can be sacrificed to destroy something are not that good either to be very much worth considering as well. Yahenni is a good sack outlet, indeed, and IMHO in a good way different from Viscera Seer (in the context of increasing efficiency of Fatal Push).

Fatal push would benefit from fetchlands or sacklands greatly.
Can you comment butcher ghoul vs Geralf's Messenger?
Sultai Emissary is definitely a interesting choice, interesting in good sense.
Festering Mummy has an analogue Festering Goblin (just said)
Death Baron and Grave Pact would have malevolent synergy.

The deck name catched attention and could not resist to take a look and then comment.

The prot red prot white knight could be also quite good in some metas. Flagstones of Trokair could protect against some contingencies as would Runed Halo. I wonder if an enchantment search (or scry, although Crystal ball does not seem that good) could make deck run smoother because the Phyrexian Unlife and Solemnity combo seems essential and either one could be as dead as a card as Ackhmed as a terrorist. When the deck can shut opponent's deck off early, then some one mana alternatives to Path could be even better, although the Path can fetch a land for you.

Cool control. Prot red and black knight might also work well in some metas. Flagstones of Trokair would help against some contingencies, as would Runed Halo. Phyrexian Unlife and Solemnity combo shuts down many decks, if it is very important, then perhaps some scry cards (Crystal ball sucks, anything better there?) or enchantment search would make the deck run smoother.

edit: deleted

Can you post the illegal deck then for reference?

While you already have the best pump for the deck, you may at least glance over Seal of Strength and Blossoming Defense.

Asceticism I have not tested myself because I went to Collected Company route and hence have everything else less than 4cc except a single copy of Nylea. I have no elephant but 3x or 4x Rancor and a pair of Champion of Lambholts for evasion, instead. Collected company is not Ghalta but I admit that Ghalta seems more fun.

I also wonder whether Khalni Hydra would work for insane devotion combo. Alas, if it starts to rely on that combo, then the deck probably needs some more evasion than late elephant combo such as Birds of Paradise, Champion of Lambholt or a full playset of Rancor.

Title is misspelled as 'Gahlta'

Ornithopter's strength as the first-drop (0 mana) would be maximized if you used 1-mana utilities such as Inquisition of Kozilek or Opt.

Triton Shorestalker is 1/1 unblockable. Judge's Familiar is just a 1/1 flier but it's activated ability might at least delay some early counter-strategies.

If some chance removal or bounce is needed, a single Tragic Slip or even Mark of Eviction, perhaps.

Modern Legal:
-2 engineered plague
-1 Volrath's Stronghold
+2 Death's Shadow
+1 Swamp

+1 at that (Blossoming Defense, for example, unless it is budget theme also)

-1 Angel of Salvation
+1 Harmonize
---------------------------------
Total: 1x Angel of Salvation, 2x Harmonize, perhaps? Reason: Consistency.

Mirri, Weatherlight Duelist ?

Yes. I am sort of synergy fan, it creates sort of theme and it feels very elegant.

Soul Stair Expedition could interact well with Bloodstained Mire.
Alternative to Soul Stair Expedition is Oversold Cemetery. However, it would interact very well with Vexing Devil I previously commented in association with theme. Theme is a question of name magic, of course.

Other cards to consider:
Dreadbore - getting rid of planeswalkers
Liliana of the Veil - sacrifice theme and a powerup, possibly
Nether traitor - good for sacrifice, good for devotion
Bloodthrone vampire - sacrifice enabler, threat
Devour flesh - interesting Trixxor: life gain and sacrifice enabler or, situational excellent removal
Diabolic Intent - sacrifice theme search
Disciple of Griselbrand - sacrifice enabler / lifegain
Grave Peril - devotion/sac-removal
Nezumi Bone-reader -sacrifice enabler / discard
Soldevi Adnate - sacrifice enabler for Keldon Marauders or late game Fulminator Mage
Torment of Hailfire - multiplayer?
Bloodchief Ascension - midrange strat
Deathgreeter - life gain 1stdrop if needed