Today we continue our look at the spawn of the Far Realm with the gibbering mouther, a weird and horrifying denizen of places no one in his or her right mind would go, and where no one stays in his or her right mind for long. An oozing blob dotted with mouths full of teeth and horrifying noises, the gibbering mouther offers an interesting analytical challenge, as its stat block looks unlike anything we’ve examined so far.

The gibbering mouther has average Strength, very high Constitution and low Dexterity, an atypical ability contour. It’s not strong enough to be a brute, it’s not fast enough to be scrappy, and it has no aptitude for stealth. Its low Dexterity suggests that, since its ability to avoid damage is poor, it will need some kind of compensatory advantage to make combat worthwhile, and simply being able to soak up damage isn’t enough; we’ll have to look for this advantage among its other features.

Its mental abilities are typical of an animal: average Wisdom (reflecting little except its perceptive ability), low Charisma and very low Intelligence. Entirely instinct-bound, it makes no distinctions of any kind between potential targets; one is as good as another. It may sometimes retreat when injured, but that’s the extent of its ability to adapt to changed circumstances.

Aside from its darkvision (necessary for a subterranean dweller), it has no skills, vulnerabilities, resistances, immunities (except to being knocked prone, since it’s amorphous) or unique senses. It can’t speak or comprehend speech. Its most distinctive features are Aberrant Ground, Gibbering and Blinding Spittle:

  • Aberrant Ground handicaps melee attackers by causing the terrain around the gibbering mouther to soften and heave. Enemies who fail their Strength saving throws are unable to move; enemies who succeed are slowed by half, unless they have the ability to negotiate difficult terrain at full speed.
  • Gibbering causes an effect similar to that of the confusion spell in enemies within 20 feet who fail their Wisdom saves.
  • Blinding Spittle is a ranged, area-effect attack with a radius of only 5 feet, thus affecting only one target in most cases. On a failed Dexterity save, it causes the blinded condition, but it does no damage.

Remarkably, given these unique features, the gibbering mouther’s real strength seems to lie in its bite attack. It does a whopping 5d6 piercing damage and can also knock an enemy prone. There’s that compensatory advantage we were looking for.

So how do these fit together? Of the gibbering mouther’s four features, two—its bite and its Blinding Spittle—can impose debilitating conditions. The blinded condition gives a target disadvantage on attacks and gives enemies advantage on attacks against him or her. Prone does the same, except that only attackers within 5 feet of the target have advantage on attacks against him or her; attackers from farther away have disadvantage. But the gibbering mouther’s only direct attack is a melee attack, so that’s not a problem for it. Ideally, therefore, the mouther wants to blind a victim or knock it down, then chomp on it. This means that when it Multiattacks, it uses its Blinding Spittle first (if it’s available) and bites afterward.

But what about the other two features? They don’t offer the mouther any advantage on its attacks, their saving throw DCs are paltry, and the effect of Gibbering can’t even be relied on.

Their impact is measured by their ability to keep allies of the mouther’s victims from fighting back. Once the mouther has blinded a victim and is moving in to devour it, it wants to be able to do so without interference. Both Aberrant Ground and Gibbering discourage would-be melee attackers from getting too close; if one does approach and engage, Gibbering causes him or her to do something other than attack the mouther between 25 and 40 percent of the time, roughly.

The real mystery is why anyone would get within 15 feet of a gibbering mouther (the range of its Blinding Spittle) in the first place. It can sense potential prey up to 60 feet away, and there’s nothing to suggest that it wouldn’t reflexively start making horrific noises as soon as anyone came within range. It can move only 10 feet per round. It’s not stealthy. It’s not smart enough to lay traps. How can it hunt when the only reasonable reaction to it is to run the hell away?

Here’s the best answer I can come up with: It swims. According to the Monster Manual flavor text, the gibbering mouther “swims through water, mud and quicksand with ease.” There’s your element of surprise. A gibbering mouther can’t conceal itself in plain sight, but it can hide unseen and unheard in mud, muck, quicksand or dark water. When prey passes by, out it pops, discharging its Blinding Spittle at the easiest target it spots.

The gibbering mouther seemingly ought to flee when it’s seriously injured (reduced to 26 hp or fewer), but none of the three basic flight actions—Dodge, Dash and Disengage—works all that well for it. It’s neither smart enough to Disengage nor fast enough to get good use out of it. Its armor class isn’t high enough to make Dodge worthwhile, nor does it have any reason to prolong a losing battle. And its Dash distance is less than most PCs’ base movement speed.  I’d conclude, therefore, that it fights to the death simply because it has no good way of not fighting to the death, and its best (and, really, only) hope is to land lots of bite attacks and hope that its other abilities keep the aggro off.

What’s really going to ruin a gibbering mouther’s day, even more than being seriously injured in melee combat, is any kind of ranged attack—weapon or spell. It has no way of countering such a thing; it may not even understand what’s happening, especially if the attack comes from farther than 60 feet away. If the mouther takes damage from one of these sources, doesn’t already have an enemy blinded or knocked down, and isn’t engaged in combat with a melee opponent, it will Dash (action) in the opposite direction of wherever the attack came from.

Next: oni.

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