What if you’re a wizard with the ego, ambition and power to pursue immortality through self-enlichment, and you start the grueling process but fail to pace yourself properly? You could end up as a boneclaw, the powerful undead servant of a random individual who certainly didn’t ask for one and may or may not have any use for it.
Figuring that only the most brilliant mages even have a chance at becoming liches, the boneclaw’s Intelligence of 13 is surprisingly low, and I ascribe this to the trauma of failure. Something about the process of becoming a boneclaw damages the erstwhile wizard’s intellect, surely a sore spot. It’s not stupid by any stretch, just unable to soar to its previous heights of brilliance. Its Intelligence is now outshone by its extraordinary Strength and very high Dexterity, Constitution and Wisdom.
Those latter three high stats are accompanied by proficiencies in their respective saving throws, meaning that the boneclaw possesses exceptional resistance to the vast majority of attacks that require saving throws to resist. It may not be able to perform the kind of magic it once did, but your magic isn’t going to impress it one bit.
Proficiency in Perception and Stealth gives it the toolkit of an ambush attacker, and if we designate Strength as its primary offensive ability and Dexterity as its primary defensive ability, what we have is a nasty shock attacker that’s going to strive to maximize its first- and second-round damage. It can stay in the fight longer, because of those great saving throw modifiers; its resistance to cold and necrotic damage and to physical damage from nonmagical attacks; and its immunity to being charmed, exhausted, frightened, paralyzed or poisoned. But its preference is for swift and deadly strikes.
It also prefers to strike at night. With 60 feet of darkvision plus the Shadow Stealth and Shadow Jump features, the boneclaw has no business going around in broad daylight. It’s a nocturnal and subterranean predator.
The boneclaw has two actions to choose from, Piercing Claw (or a Multiattack comprising two of this action) and Shadow Jump. Of these two, Shadow Jump is unambiguously an exit maneuver, since it inflicts necrotic damage on every creature adjacent to the boneclaw; there’s no benefit in doing that on your way into a combat encounter. Therefore, the boneclaw will always lead off with a Multiattack while unseen. Ideally, it will do this while remaining in dim light or darkness, so that it can immediately use Shadow Stealth to Hide itself again as a bonus action; this way, it hopes to get its next attack while unseen as well.
Note that the reach on its Piercing Claw is an insane 15 feet. The boneclaw’s target doesn’t have to be adjacent to it—it can strike someone from across a room, at least a room the size of the room I’m in now, then pull it to its own side. If the target tears free and tries to run, the boneclaw can hit it with an opportunity attack, then overtake it with its 40-foot movement speed. If an ally of the target rushes to his or her defense, the boneclaw gets a free hit as soon as he or she enters its reach, courtesy of Deadly Reach.
So when to use Shadow Jump? Well, if the boneclaw has only one adjacent enemy, it’s probably focusing on tearing him or her to shreds. If it has two, it has at least a chance of grappling the second opponent as well, although it may or may not want to, depending on the will of its master. With three adjacent enemies, however, it’s literally got its hands full. At that point, it makes a snap judgment about which of its grappled opponents it hates more and zops away to a better location, taking that opponent with it.
The biggest risk the boneclaw faces is the opponent who cleverly decides to drench it in light, denying it the ability to take advantage of Shadow Jump or Shadow Stealth. Its Piercing Claw deals an average of 20 damage on a hit, which isn’t enough to improve the chances of disrupting a spellcaster’s concentration. Against an opponent holding a lantern, torch or flare, it could take advantage of the little-known but highly satisfying Disarm action rule on page 271 of the Dungeon Master’s Guide, but knocking the light source on the floor won’t necessarily extinguish it or cast the boneclaw back into shadow.
So, probably, the boneclaw will react to bright light simply by moving posthaste to the nearest place of shadow, wherever that may be, using the Dash action if need be and not giving a hoot about opportunity attacks, so that it can use Shadow Stealth to get out of sight again. If it has movement left, it will use that movement to keep going just in case someone shines a light on the place where it vanished.
The boneclaw has no reason to flee, ever, because thanks to Rejuvenation, it simply can’t be killed unless its master is killed (or repents and renounces evil forever, which is less likely). Even then, it’s probably so out of the habit of thinking about its own self-preservation that it still won’t bother to run away to save itself. Nevertheless, it does have a high Wisdom, which raises the question: for what? Probably not for deciding when it should parley, because Charisma is its dump stat. Probably not for hesitating before attacking a powerful group, because it’s more about deadly nova strikes than sober risk assessment. Most likely, it’s for target selection, assuming that its master allows it any leeway in this regard; for choosing the best place and time to strike; and for having a planned route of departure.
Even so, after a boneclaw has spent a couple of rounds brutalizing a victim, it doesn’t especially care to stick around and deal with that victim’s allies. Thus, starting in round 3, it follows its chosen exit path, taking its victim with it if it can. If the victim gets away, then who knows—maybe that boneclaw will come back to play some more a few rounds later. The player characters will certainly tire of this long before the boneclaw does.