Time for another oldie but goodie: the slithering tracker, one of the Advanced Dungeons & Dragons Monster Manual’s original oozes. Mind you, back then, “ooze” wasn’t a monster category; certain monsters simply happened to be oozy by nature. Also, it was smaller: only 2½ feet long. (It’s Medium-size now.)
A curious thing about the slithering tracker is that its lore has also been changed: it’s no longer a mere denizen of the underdark but the product of a nasty magical transformation, the sort that usually produces something undead, and rather than simply hunt prey to consume, it actively seeks vengeance. However, unlike, say, a revenant, once a slithering tracker sucks the life out of its target, it doesn’t consider its mission fulfilled. Instead, it keeps compulsively sucking life from whatever other beings it can suck life from until it’s put out of its misery.
For this reason, you can’t treat a slithering tracker like any other ooze. It’s much more akin to the undead, in the sense that it’s driven by a compulsion that it can’t control and that overrides its survival instinct, despite its high Wisdom.
For a being made of supernatural jelly, the slithering tracker has astonishingly impressive physical ability scores: its Dexterity is extraordinary, and both its Strength and its Constitution are very high as well. Its Intelligence is humanoid-average. Although it lacks proficiency in Perception, it has 120 feet of blindsight, and this combined with expertise in Stealth, the ability to climb and swim, and a collection of other traits ought to make it a consummate ambush attacker that finishes its primary victim off in a turn or two.
And yet there’s an internal contradiction in its abilities that undermines its potential effectiveness somewhat. The Ambusher trait gives it advantage on its first-round attack roll against a surprised target, but the action it really ought to take in its first round of combat is Life Leech, which restrains its target and deals ongoing necrotic damage—but calls for a saving throw to resist, which forfeits the benefit of Ambusher.
Let’s assume that a slithering tracker has a 65 percent chance of hitting its target, that its target has a 50 percent chance of making its saving throw, and that it always gets to make that first attack with surprise. How, then, does using Life Leech right away compare with first using Slam in round 1? We’ll look at just three rounds of combat, since the slithering tracker wants this fight to be over fast.
By increasing the probability of a first-round hit from 65 percent to nearly 88 percent, using Ambusher deals roughly an additional 2 damage, on average, over waiting to use Slam until round 2. However, using Life Leech right away allows the possibility of an additional round’s worth of necrotic damage, which more than makes up for it. The net result is that the damage difference between the two sequences is insignificant: accounting for the probability of escape from the grapple/restraint, each can be expected to deal about 26 damage over three rounds.
To look at it another way, however, the competitiveness of Life Leech depends on its target’s failing that first saving throw. If they succeed instead, you can scratch off all the necrotic damage that Life leech would deal, and the opportunity to gain advantage on a round 1 Slam attack is lost. So that seems to be an argument for seizing the chance to Slam with advantage in the first round. Life Leech can still fail in later rounds, but at least the opportunity cost is lower.
How much of a difference does it make if the target’s Armor Class or saving throw modifier is lower or higher? Algebra time! The result is that it’s better to Leech first and Slam later when s > 3√([−8.5a2 + 8.5a]/[−8.5a2 + 8.5a + 16.5]), where a is the chance of hitting on an attack roll and s is the chance that the target fails their saving throw. (Trust me, it looks even worse if you solve for a.) But check this out: If you try this equation on any AC that a low-level player character is likely to have (10 to 18), s is always between 40 and 50 percent, and usually between 45 and 50 percent—in other words, the inflection point is somewhere between a saving throw modifier of +2 and one of +3 or +4.
Who’s going to have a Dexterity save mod of +3 or higher, or AC 10 or 11 and a Dex save mod of +4 or higher? The latter is easy to answer: Almost nobody. It’s nearly impossible to have a Dex save mod of +4 and not have a better AC than 11 while wearing no armor. [ETA: It’s technically possible, though not terribly likely, that a level 10 or higher bard might choose both to have a Dex of 13 or lower and to wear no armor. Such choices would undoubtedly lead them to die an avoidable death long before encountering a slithering tracker.] As for the former, bards, monks, rangers and rogues have proficiency on Dex saves, making these classes the most likely to have a Dex save mod of +3 or higher; otherwise, you’re mainly looking at spellcasters or marksman fighters with Dexterity 16 or greater, and these will usually be humans, elves, halflings or forest gnomes.
With Intelligence 10, a slithering tracker can recognize a target’s race and easily determine their class, but reading their exact Dex score is beyond it. So this long and winding journey brings us to the conclusion that a slithering tracker leads with a Slam attack against a bard, monk, ranger or rogue; a human, elf, halfling or forest gnome wielding a bow or crossbow; or an elf or halfling backline spellcaster. Against anyone else, the potential extra round of necrotic damage is enough for it to forgo the benefit of its Ambusher trait and use Life Leech immediately.
False Appearance, Spider Climb and Watery Stealth allow slithering trackers to lie in wait in a variety of nasty places: muddy roads, slimy cavern ceilings, rafters, rain gutters (really, anyplace overhead—if you’ve played Overwatch, you know that nobody ever looks up), docks, wells, fountains, horse troughs. When a victim comes within reach, a slithering tracker initiates combat as described above. If it hasn’t killed its target in three rounds, or if it tries to use Life Leech and fails, it Disengages and retreats to the nearest safe hiding place (Liquid Form lets it slip through a 1-inch crack), taking full advantage of its climbing and swimming speeds to elude pursuers. Once hidden, it uses its best judgment (which is pretty good, given its high Wisdom) to determine whether it’s worth sticking around and finishing the job or better to try again later. If it took damage in the fight, it’s more likely to wait; if its victim and their defenders seemed pretty hapless, it’s more likely to stick around and strike again.
What about if the slithering tracker is seriously wounded? This is a tough call. Revenge is easier to take when you’re not dead, and its Wisdom suggests that it should grasp that. But as I mentioned, the manner of its creation suggests that its drive to attack is compulsive, especially if it’s already achieved the revenge it sought to take in the first place, so maybe it can’t bring itself to retreat when its life is on the line. It may even vary from slithering tracker to slithering tracker. I’d say that the more a given slithering tracker has succumbed to insanity and bloodlust, the less likely it is to withdraw to save itself. If you decide that your slithering tracker is more mission-oriented and willing to take a loss today if it means a win tomorrow, the threshold for departure is when it’s reduced to 12 hp or fewer.
Next: yeth hounds.