Need something to go with your walking brain? How about a hovering brain with stinging tentacles? OK, technically, a grell’s body only looks like a big brain, according to game lore, but it does originate from the Far Realm—also the home plane of the mind flayer and the intellect devourer—so if you need another aberration to round out an encounter with these psionic nemeses, the grell is a good fit.
Grells are above average in all their physical abilities, but the balance is tipped toward Strength, with Dexterity coming in second, suggesting a hit-and-run attacker. Their primary mode of movement is flying, with the ability to hover, and they have high proficiency in Stealth.
One thing they don’t have, however, is much flexibility. Beyond its unexplained immunity to lightning and its ability to sense without eyes, the grell’s features are limited to a simple Multiattack comprising one attack with its beak and one with its tentacles.
The tentacles are the grell’s distinguishing feature. A successful tentacle hit requires the grell’s target to make a (not very difficult) Constitution saving throw to avoid paralyzing poison; it also grapples and restrains the target. The grappled/restrained condition is the more interesting of the two. Although the grell is only a Medium-size monster itself, it can grapple and carry any Medium or smaller target.
And so the grell’s modus operandi takes shape: It hovers in the air, waiting patiently and still for a victim to pass by. It lashes out with its tentacles first, because a successful hit with the tentacle attack means advantage on the bite attack. Once it’s got hold of a victim, it doesn’t hang around—it floats off to enjoy its feast in peace. Note that this halves the grell’s speed, according to the rules of grappling, meaning that the grell’s first movement will be upward, out of reach of any other enemy. The grell is another of the odd monsters for which the Monster Manual describes tactics in the flavor text, and the tactics it describes are consistent with the pattern implied by the grell’s stat block.
Grells are intelligent creatures—as intelligent as the average adventurer—so they don’t operate solely by instinct. And they’re evolved creatures, despite having evolved on another plane of existence, so their sense of self-preservation is intact. A grell can plan and strategize, and it can recognize a situation in which attacking would be detrimental, but it’s also tough enough (against common humanoids, at least) that merely being outnumbered usually isn’t enough to deter it from attacking. It may or may not make good choices when it comes to selecting targets—it may, for instance, go after a stouthearted halfling because he or she is small, not realizing that he or she is also tough. Among grells that live in subterranean colonies, it’s common knowledge that dwarves make poor prey, owing to their resistance to poison, but a lone, feral grell or one that associates mainly with other aberrations may not be aware of this fact.
If a character can communicate with a grell (it does speak, in its own language), there may even be room for negotiation, although there’s not a whole lot they want beyond easy access to food and uncontested territory to hunt in. Also, as the MM flavor text describes, they’re not likely to see much value in negotiating with beings they classify as “edible.” If the party can somehow demonstrate that they’re “great eaters” capable of hunting and killing a grell, the prospects for negotiation are much more favorable (though not, for obvious reasons, with any grell they’ve hunted and killed to prove it).
A grell retreats when seriously injured (reduced to 22 hp or fewer), and it has the savvy to Disengage (action) from any melee opponent(s) before floating away. As it does, it may gabble out a petulant concession of defeat in its own language, offering player characters a clue that it’s capable of speech and conversation.
Next: gibbering mouthers.