The Tarkanan assassin is a hired killer, but that (plus their Dexterity and their Armor Class) is where their resemblance to the standard assassin in the Monster Manual ends. Most conspicuously, they don’t have the Assassinate trait—or even Sneak Attack! Clearly, this non-player character requires a fresh approach.
As one might expect, the Tarkanan assassin is a shock attacker, with a decent enough Constitution to put up with a bit of a scuffle but primarily interested in getting in and out of combat quickly. Proficient in Athletics instead of Acrobatics, they’re more likely to tackle their target than shoot them while hanging upside-down outside a window. They’re also proficient in Sleight of Hand, perhaps for slipping poison into someone’s drink—it’s not enough by itself to conceal spellcasting. Deception proficiency suggests an aptitude for disguise, and Perception plus Stealth is the hallmark of the ambush attacker.
Tarkanan assassins have darkvision, which is interesting, because House Tarkanan, according to the lore in Eberron: Rising From the Last War (chapter 4, “Crime in Sharn: House Tarkanan”), comprises members of many races, not just those with darkvision. Does this mean that House Tarkanan doesn’t employ humans, halflings or changelings as assassins (and why wouldn’t you hire changelings to perform all your asassinations?), do they somehow acquire darkvision as part of their initiation into the order of assassins, or is it an unmentioned side effect of their aberrant dragonmarks? The book doesn’t say. Choose your own favorite explanation.
Unlike the vanilla assassin, Tarkanan assassins possess a small amount of innate magical ability: the power to cast fire bolt (or, alternatively, a different cantrip) at will and a 2nd-level chromatic orb (or a different 2nd-level spell) once per day. These are both ranged spells, not suitable for close quarters.
The Tarkanan assassin does possess a melee Multiattack, two Shortsword attacks that deal additional poison damage, and the fact that they use a finesse weapon is consistent with their reliance on Dex. But I get the sense that the stab in the back is just one of several tools in their kit, and probably not their favorite. If you’re trying to murder someone, you don’t want to be close to them if your initial attempt fails. On the other hand, two Shortsword hits, juiced up with poison, deal an average of 27 total damage, enough to kill your run-of-the-mill noble outright.
But we can game these abilities a bit and find a sweet spot that offers the best of both worlds, thanks to the Unstable Mark trait, which deals force damage in a 10-foot radius around the Tarkanan assassin whenever they cast one of their innate spells. Let’s say that they start combat by sneaking up to a distance of 10 feet from their target—close enough to deal a bit of additional damage to the target with Unstable Mark, far enough away that they don’t have disadvantage on a ranged spell attack—and lead with fire bolt.
If this doesn’t bring the target down—and if they’re any more formidable than a typical commoner or noble, it probably won’t—then the target’s reaction determines their next action. If the target runs toward them to start a fight, they retaliate with a melee Multiattack. If the target runs away, they hurl a chromatic orb at them if they can get a nice, clear shot, or another fire bolt otherwise.
A sidebar offers a table of alternatives to fire bolt and chromatic orb. Shocking grasp is touch-required, so the Tarkanan assassin will have to lurk in a doorway and wait for its target to pass within reach. Poison spray requires a saving throw, so the Tarkanan assassin gains no attack roll advantage from being hidden, only the element of surprise. Friends is a clever way to improve the Tarkanan assassin’s disguise by granting advantage on their Deception check, allowing them to walk right up to their target, say, “Hey there, chum!” and then stab them in the gut. Minor illusion and dancing lights are chancy, since there’s no guaranteeing how the target will react to them. But with respect to minor illusion, in general, a sound people can’t see is more convincing than a vision they can’t hear.
Burning hands seems to contain a typo: All the other spells in this list are 1st-level spells boosted to 2nd level (as implied by their effects), but burning hands is just the straight 1st-level burning hands. It should probably deal 4d6 damage rather than 3d6. Even so, it’s not a spell for an assassin: It lacks precision, and there’s no way for the caster to improve their chances of success. (In contrast, chromatic orb and ray of sickness are spell attacks.) Thunderwave is even less apt, having the same drawbacks plus dealing poor damage and making a whole lot of conspicuous noise; it doesn’t even knock targets prone. Charm person is just supercharged friends, superseding the need for a disguise. Sleep can be an amusing way to clear the area around a robust target by causing everyone around them to pass out.
But I think there’s a missed opportunity here. Since chromatic orb can deal acid, cold, fire, lightning, poison or thunder damage—caster’s choice—why not give them an at-will cantrip that deals one of these damage types and let its element be their signature? Fire bolt and shocking grasp, sure, but instead of minor illusion and dancing lights, how about ray of frost, primal savagery and booming blade?
In fact, given that a hit with ray of frost slows its target, this cantrip would be a beauty for the Tarkanan assassin. It could lead with ray of frost cast from 10 feet away; if the spell attack hit, the assassin could then chase their opponent down and stab them to death for the best per-turn damage available to them. If the spell attack missed, the assassin could lob a cold chromatic orb at them as they fled. Just something to think about.
The Tarkanan assassin wants to spend no more time than necessary taking out its target: two turns against an unsurprised target, max. Whether or not it’s done by then, it Disengages if it’s within melee reach of more than one opponent, Dashes otherwise, moves away at full speed and tries to vanish—around a corner, into a crowd or into the shadows.
Next: warforged soldiers.