NOTE: Before you share your feedback,keep in mind that this is just an experimental build intended to imitate the Stalker's attributes and abilities. I will explain everything further below.

The Mods:

Aura: [Corrosive Projection] or [Energy Siphon],I recommend both,however the choice between the two is up to you.

Exilus: [Power Drift],[Cunning Drift] or [Stealth Drift]. I recommend these three but choice is yours.

The overall mods:
I chose [Armored Agility] to give him a slightly improved armor as well as movement speed.

I assume that the Stalker might also have some kind of Tau resistance because his suit might be an umbral frame so I gave this build two umbral mods.

[Rapid Resilience] since the Stalker is said to be immune from status effects.

[Blind Rage] for the extra strength however at the cost of efficiency. Although efficiency may be important for reducing the cost of your abilities,putting a maxed [Streamline] can counter the effect.

The rest of the mods are beneficial for this imitation build.

The Arcanes:

I recommend the following: Arcane [Guardian],Arcane Grace,Arcane Energize or Arcane Ultimatum.

The Arcane Ultimatum can be useful when using Radial Blind.

Arcane Energize can be useful with keeping your energy bar full.

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The Abilities
Another Note: Since we are limited in terms of abilities and subsumed abilities,I had to be creative and resourceful over Excal's powers to imitate Stalker.

Slash Dash is one of Stalker's abilities. We have no problem here.

Radial Blind can be used like Stalker's Dispel except that it doesn't actually dispel enemy abilities but still useful for disabling and stunning enemies nevertheless just like Stalker's Smoke Screen and Teleport.

Radial Javelin can be used for lower levels for CC or just another stun ability in high levels like Stalker's version of Reckoning to [Negate] incoming damage by staggering enemies,paired with Radial Blind.

I replaced [Exalted Blade] with Defy to imitate Stalker's Absorb. We don't need the highest range for this ability since we wouldn't be stationary in the first place.

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My thoughts on this build:
I got inspired to create this experimental build because I'm a fan of Stalker ingame,okay I might be edgy but that doesn't mean I'm dumb because as I said,this is just an experiment to imitate Stalker using [Excalibur].
As you can see,many might say "Why replace [Exalted Blade] with Defy instead of replacing the useless third ability aka RJ instead?" Like come on,I know many people say that RJ is useless but not really,I still find it useful in levels below 30 and also no offense but I find it absurd to see a Stalker cosplayer spam EB using Excal while almost ignoring the other abilities.
The reason I decided to keep RJ is because I don't want to spam Defy in lower levels for CC as well as to imitate Stalker's Reckoning paired with Radial Blind.--

This guide will be updated again soon (The build needs more testing for now.)