By Alan McCoy from Dungeons & Dragons: Fundamentals
How to build challenging encounters against a Grell
Note: This has been prepared utilizing only the 5E Core Rules. The Grell can be found in the Monster Manual page 172.
The Grell is a medium sized aberration that has the appearance of a bulbous floating brain, with a wide sharp beak, it has many long tentacles that hang beneath. It can fly and hover unmoving.
The Grell have no eyes and rely on their keen hearing and can sense changes in electrical fields, this allows them to detect the presence of creatures and objects in near proximity.
The Grell would be considered a typical ambush predator except for the fact that it is SMART, as in smarter than most people. The Grell use their intelligence to help them isolate their next meal while avoiding retaliatory combat. Grell prefer to avoid open conflict and are patient, waiting for the opportunity to ambush a straggler, or someone not in direct contact with others of their group.
The Grell usually solitary, but sometimes gather in small groups referred to as a “Float” (Note: the MM calls a group a “Coven” for some odd reason, I refuse to belittle that term.), these creatures have their own language, which is based on electrical impulses and vibrations, rather than speech and sound.
While Grell conversation would probably be strange to any humanoid, they do seem to communicate status of hunting areas: poor, fair, good, hostile, etc. Grell are also known to communicate the presence of any conflict within their hunting area. The Grell with then decide, singly or as a group to steer clear of any major conflict in their environment, how best to remain unseen and undetected, until the time is right to pick off the isolated straggler.
Grell society categorizes the creatures of the world into three distinct groups: Edibles – Those that can picked up and carried off without trouble, this includes all small or medium sized creatures weighing 225 pounds or less, and given sufficient time and isolation, can include creatures weighing up to 450 pounds. Inedible – Including all Large size creatures or bigger, or those that have enough defenses to give the intelligent Grell pause. Great Eaters – those creatures that can prey on a Grell.
An individual Grell lair is usually a hidden alcove or other perch virtually inaccessible to those without the ability to fly.
Step 1) Let’s Review what we know about the Grell
Grell can fly and hover up to 30 feet per round.
Grell have high Strength and Dexterity, above average Constitution, Intelligence and Wisdom, and a below average Charisma.
Grell are Proficient in the skills Perception and Stealth.
Grell are IMMUNE to Lightning Damage.
Grell cannot be Blinded or Knocked Prone.
Grell have Blindsight 60-foot though they are blind beyond this radius, and a passive perception of 14.
Step 2) Determine the probable Strategy
Grell are intelligent predators, floating ambushers who wait until they find an isolated target who they can drop down on, quickly poison, and then lift away to its lair to consume at its leisure. They do not attack groups unless in groups themselves.
Step 3) Determine Tactics
Using their proficiency in stealth, the Grell will fashion a HIDE from which they can observe an area and search for prey. Once suitable prey has been detected, the Grell will drop down upon it wrapping multiple tentacles around the prey and injecting it via those tentacles with a paralytic poison.
Tentacles engaging the target are left in place to grapple the target, while fresh tentacles are placed to pump even more poison into the target.
Once the target is paralyzed, and thus firmly grappled, it will be lifted and taken to the lair.
Should a Target begin the recover from the paralytic while in flight, the Grell will drop them and allow the fall damage to weaken or kill the prey before grappling them once more to enjoy its meal.
Step 4) DM Tips and Observations
The AC of this creature is way too low. Bring that up, call it a natural field of energy like Mage Armor but with a base AC 13) and combine with their dexterity for a final AC of 15.
The Grapple of this creature and lifting capacity is its primary feeding characteristic, and it has a Strength of 15? Make it 16, but to avoid changing characteristics overmuch, make its tentacle attacks DEXTERITY Based.
The DC of the Poison is too low to be effective against Player Characters: I would raise this from the current DC 11 to a DC 13.
The Grell has 10 tentacles with a 10-foot reach, yet it’s multi-attack specifically states that it must attack with ONE tentacle and its beak with a 5-foot reach. I would state that the Grell probably doesn’t use the Beak to fight at all, just to feed. I would allow the Multi-Attack to be with two Tentacles or with the beak against a Paralyzed opponent.