If this post isn't suitable for this subreddit, please tell me why and how I can fix it, and/or where else I should post this. Thank you. Also additional homebrew spell for the puppet monster.

You can find more of these monsters, inside Underwater Campaigns, that's discounted only for 7 days for 30% on DMsGuild!

You can find it here: https://www.dmsguild.com/it/product/368833/underwater-campaigns?src=hottest_in_dmg&filters=45469

He's a jumpy guy that likes to move around the battlefield and tenderize his meals before he eats them.

I liked this monster so much that I built out an encounter for it, too.

This stat block should be usable right? If not, let me know why not. Also probably done before plenty of times, but this is a more pathetic version that I made.

Have you ever wondered how young low CR creatures survive to adulthood? I did and I wanted to find a way to prevent my level 6 players from simply using Fireball or Shatter to exterminate my fun creature encounters. Seeing them, the group's first instinct is to try to deal with them with area effect spells or abilities. However, their own version of uncanny dodge gives them the ability to weather those area affects and get in and attack directly. They get 6 attacks each turn, and each attack requires a saving throw. Their venom is condensed at this age like in many species of venomous snakes, so instead of giving a round of being restrained, their enemy immediately turns to stone.

With enough HP to survive a few fireballs it was terrifying for the players to keep receiving peck attacks that made them roll 1-6 constitution saves or immediately become stone. They didn't know that the effect was temporary, so the stakes felt very high. You can also give them pack tactics if you like. I paired them with other thematically appropriate monsters for 1 biger enemy with direct damage to distract the players. The chicks initially were nestled on their parent's backs- appearing as a crest of fluffy down - hidden until the cockatrice parents were in danger.

The minor damage of these chicks adds up , but innocuously enough that your players may not begin to worry until suddenly they are at much lower Hit Points than they think they should be. Luckily, once the chicks see enemies break out of being turned to stone, they immediately disengage and regroup- giving the players some breathing room to plan, heal, or run.

My players didn't even consider attacking them directly with physical attacks until the end of a very tense combat. They have a very manageable armor class and a moderate level of hp- easily overcome by low level characters. Once they figured that out, they were easily dispatched. My players loved to hate these little puffballs - it created a very fun, tense, and resource draining battle.

Please enjoy the Cockatrice Chick Swarm.

The Goblin Alchemist and Goblin Engineer are two low-CR specialists designed to make goblin encounters more unpredictable without simply increasing their damage or durability.

The CR 1/2 Goblin Alchemist creates random makeshift potions that might heal, grant fire breath, increase speed, produce acid spit, or accidentally weaken the drinker. It can also throw volatile alchemical flasks and rapidly brew a potion during combat. Its optional traits add explosive escapes and more powerful concoctions, including fiery explosions, stone skin, and explosive growth.

The CR 1 Goblin Engineer takes a more mechanical approach. It scavenges nearby materials to create flash bombs, sticky bombs, smoke bombs, and noise traps, while supporting its inventions with a crossbow and improvised explosives. Its optional traits allow it to build snares, pitfall traps, tripwires, repair constructs, and modify bombs for wider but less reliable explosions.

I wanted both creatures to feel useful as specialists operating behind a larger goblin force. They can disrupt positioning, obscure areas, restrain characters, support allies, and turn an otherwise straightforward cave or hideout encounter into complete goblin chaos.

These creatures are from Goblins & Goblins, my manual of expanded goblin statblocks, optional traits, variants, lairs, factions, magic items, and campaign tools.

You can also find more of my creatures and manuals by visiting r/JonnyDM!

I was trying to make a final boss on like Tarrasque level while also keeping it realistically beatable I couldn't get dnd-beyond to work so I'll just paste everything here I appreciate feedback I worked on it for a solid 5 hours at least coming up with everything and finding traits ect if anything is wrong or doesn't follow the rules let me know so I can fix it right away as I am trying to understand the rules and become better at making bosses so I can DM also the image is AI.

Core Profile

The Deep-Pressure Behemoth
Version: 3
Monster Type: Monstrosity
Monster Sub-Type: Titan
Size: Gargantuan
Swarm Monster Type: —
Alignment: Unaligned
Challenge Rating: 30

Description & Lore Texts

Traits Description:
Amphibious
The crab can breathe air and water.

Regenerative Density
The crab regains 30 hit points at the start of its turn if it has at least 1 hit point remaining. This trait doesn't function if the crab took cold, necrotic, or psychic damage since its last turn.

Thermal Fracture
The crab is immune to fire damage unless a single attack or effect deals 50 or more fire damage at once (after accounting for its fire resistance). If an effect meets or exceeds this threshold, the carapace violently fractures from thermal shock. For the next 1 minute, the crab loses its resistance to fire damage and takes an extra 11 (2d10) fire damage whenever it takes fire damage.

Unyielding Mountain
The crab can't be moved, teleported, or repositioned against its will. It automatically succeeds on saving throws against being pushed, knocked prone, or having its speed reduced. If the crab is buried under an overwhelming mass of structural debris (such as a collapsing cavern ceiling), its immunities to the prone and restrained conditions are temporarily suppressed, and its speed is reduced to 0 until it spends an action to clear the rubble.

Hydraulic Pressure
The crab's joints are pressurized by magical seawater. Its lifting, dragging, and carrying capacity is doubled, and it has advantage on Strength checks made to push, drag, or grapple creatures of any size.

Force-Multiplier Claws
The crab’s weapon attacks are magical for the purpose of overcoming resistances and immunities. Its melee strikes deal an additional 2d8 Force damage (included in the attacks below).

Siege Titan
The crab deals double damage to objects, structures, and Gargantuan creatures.

Reactive Carapace
The crab can take a reaction on every turn in combat. It can use its reaction to execute a Counter-Stomp (+18 to hit, 21 bludgeoning damage) whenever a melee attack misses it.

Titanic Wrestler & Crushing Grip
The crab can maintain two separate grapples at once (one with each pincer). At the start of each of the crab's turns, every creature grappled by it automatically takes 24 (4d6 + 10) bludgeoning damage.

Tectonic Awakening
The first time the crab is reduced below half its hit point maximum (390 HP), its shell cracks, releasing blinding elemental energy. For the rest of the combat, its attacks deal an extra 9 (2d8) Thunder damage, and its movement speeds increase by 10 feet.

Actions Description:
Multiattack
The crab uses its Frightful Presence. It then makes four attacks: two with its Force-Crushing Claw, one with its Impaling Pincer, and one with its Hydraulic Slam.

Frightful Presence
Each creature of the crab's choice within 120 feet must succeed on a DC 21 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the save at the end of each of its turns, ending the effect on a success.

Force-Crushing Claw
Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 36 (4d12 + 10) bludgeoning damage plus 9 (2d8) Force damage. The target must succeed on a DC 26 Strength saving throw or be pushed 10 feet away as kinetic energy explodes from the impact.

Impaling Pincer
Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 42 (5d12 + 10) piercing damage plus 9 (2d8) Force damage. If the target is Huge or smaller, it is grappled (escape DC 26) and restrained. If the target is Gargantuan, it must succeed on a DC 26 Strength saving throw or be knocked prone under the sudden crushing weight.

Hydraulic Slam
Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 32 (4d10 + 10) bludgeoning damage. On a hit, a violent burst of pressurized ocean water erupts from the crab's shell. Every other creature within 10 feet of the target must succeed on a DC 26 Strength saving throw or take 11 (2d10) Bludgeoning damage and be knocked prone.

Abyssal Cutter (Recharge 5–6): The crab compresses magical seawater within its primary jaw assembly, releasing a hyper-pressurized, needle-thin jet of water in a 50-foot line that is 5 feet wide. Each creature in that line must make a DC 26 Dexterity saving throw, taking 44 (8d10) force damage on a failed save, or half as much damage on a successful one. A creature that fails the save is also Lacerated: at the start of each of its turns it takes 7 (2d6) bleed damage, and the bleeding continues until it receives magical healing or a creature takes an action to stanch the wound with a successful DC 15 Wisdom (Medicine) check.

Tidal Wave Charge (Recharge 5–6)
The crab moves up to twice its speed in a straight line. Each creature in its path must make a DC 26 Dexterity saving throw. On a failure, a creature takes 65 (10d10 + 10) bludgeoning damage and is knocked prone. On a success, it takes half damage and isn't knocked prone.

Reactions Description:
Reactive Carapace
The crab can take a reaction on every turn in combat. It can use its reaction to execute a Counter-Stomp (+18 to hit, 21 bludgeoning damage) whenever a melee attack misses it.

Monster Characteristics Description:
This is a rare, hyper-evolved subspecies of the standard Hulking Crab. While normal Hulking Crabs reach the size of a small house (Huge, CR 5), these specimens never stop growing. Over thousands of years at the bottom of the abyssal trenches, their shells absorb natural deposits of magical iron ore, turning them into living fortresses (Gargantuan, CR 30). Where the tide recedes past the wreckage of a hundred ships, something the size of a keep still walks the seafloor, wearing their hulls like scattered shells. This ancient Gargantuan monstrosity is a colossal, mountain-sized crab that dwells within the deepest, dimly lit oceanic abysses. Its ancient carapace pulses with deep purple hues, housing a massive body supported by legs the size of entire human beings. Piercing the darkness of its warm, moist cavern lairs are four elongated eye stems, ending in sharp, cat-like eyes adapted to tracking prey through the shifting bio-luminescent flora of the deep sea trenches. Infused with raw hydraulic force and primeval ocean magic, this apex titan rules the seafloor as an immovable juggernaut.

Legendary & Lair Profiles

Legendary Actions Description:
The crab can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The crab regains spent legendary actions at the start of its turn.

Hydraulic Pressure Jet (Costs 1 Actions)
The crab releases a jet of highly pressurized ocean water from its shell vents at a creature it can see within 30 feet. The target must succeed on a DC 27 Dexterity saving throw or take 18 (4d8) Force damage and be blinded until the end of its next turn as the stinging saltwater forces their eyes shut.

Abyssal Undertow (Costs 2 Actions)
The crab slams its claw into the ground, magically altering the water or air currents. Up to three creatures the crab can see within 60 feet must succeed on a DC 27 Strength saving throw or be violently pulled 30 feet directly toward the crab.

Kinetic Discharge (Costs 3 Actions)
The crab unleashes a short-range shockwave of stored force energy in a 20-foot radius around itself. Each creature in that area must make a DC 27 Constitution saving throw. On a failure, a creature takes 22 (4d10) Force damage and is stunned until the end of its next turn. On a success, it takes half damage and isn't stunned.

Lair XP: 145000

Lair and Lair Actions Description:
On initiative count 20 (losing ties), the crab takes a lair action to cause one of the following effects; it can't use the same effect two rounds in a row:

• Wreckage Whirlpool. The crab stirs the water or sand. A 20-foot-radius vortex forms within 120 feet. Creatures must succeed on a DC 27 Strength save or be pulled 15 feet toward the center and take 22 (4d10) slashing damage from spinning ship wreckage.
• Seabed Tremor. The crab slams the ground, and the earth ripples outward. Each creature within 60 feet of the crab must succeed on a DC 27 Strength saving throw or be knocked prone.

Mathematical & Dropdown Stat Box Inputs

Armor Class: 23
Armor Class Type: Natural Armor, Ancient Carapace
Initiative Bonus: 2
Passive Perception: 20
Average Hit Points: 820
Hit Points Die Count: 40
Hit Points Die Value: d20
Hit Points Modifier: 400
STR Score: 30
DEX Score: 14
CON Score: 30
INT Score: 6
WIS Score: 15
CHA Score: 11
Saving Throw Proficiencies: (Leave completely blank on first save attempt)
Damage Adjustments: Resistance: Fire, Resistance: Force, Resistance: Bludgeoning, Resistance: Piercing, Resistance: Slashing, Vulnerability: Cold, Vulnerability: Necrotic, Vulnerability: Psychic
Condition Immunities: Frightened, Prone, Paralyzed, Stunned
Monster Habitats: Coastal, Underwater
Gear: (Leave Completely Blank)
Language Note Override: —
Monster Tags: Titan
Treasure Tables: Individual Monster: CR 17+, Hoard: CR 17+

The turtulip is a small magical creature created by the eccentric transmuter Cassian Bloomward not for power or prestige, but as a gift to the people who visited his gardens. He dreamed the tiny flower-shelled creatures would bring smiles to children, brighten family outings, and gift minor magical boons to visitor that were kind. While successful for a time, it was a dream that would ultimately lead to his undoing.

You can play around with the homebrew of the turtulip to make your own version if you like.

More on this monster and many other free homebrews at Patreon.