Large beast, neutral

Armor Class 12
Hit Points 19 (3d10 + 3)
Speed 5 ft., fly 60 ft.

STR	DEX	CON	INT	WIS	CHA
13 (+1)	15 (+2)	12 (+1)	8 (-1)	13 (+1)	10 (+0)

Saving Throws
Skills Perception +5, Stealth +4
Damage Resistances
Damage Immunities
Condition Immunities
Senses darkvision 120 ft., passive Perception 15
Languages Giant Owl, understands Common, Elvish, and Sylvan but can't speak them
Challenge 44930 (50 XP)

Flyby. The owl doesn’t provoke opportunity attacks when it flies out of an enemy’s reach.

Keen Hearing and Sight. The owl has advantage on Wisdom (Perception) checks that rely on hearing or sight.

Actions

Talons. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 8 (2d6 + 1) slashing damage. Giant owls often befriend fey and other sylvan creatures and are guardians of their woodland realms.

Medium beast, unaligned

Armor Class 14
Hit Points 11 (2d8 + 2)
Speed 30 ft., swim 30 ft.

STR	DEX	CON	INT	WIS	CHA
10 (+0)	18 (+4)	13 (+1)	2 (-4)	10 (+0)	3 (-4)

Saving Throws
Skills Perception +2
Damage Resistances
Damage Immunities
Condition Immunities
Senses blindsight 10 ft., passive Perception 12
Languages --
Challenge 44930 (50 XP)

Actions

Bite. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 6 (1d4 + 4) piercing damage, and the target must make a DC 11 Constitution saving throw, taking 10 (3d6) poison damage on a failed save, or half as much damage on a successful one.

Small beast, unaligned

Armor Class 12
Hit Points 7 (2d6)
Speed 30 ft.

STR	DEX	CON	INT	WIS	CHA
7 (-2)	15 (+2)	11 (+0)	2 (-4)	10 (+0)	4 (-3)

Saving Throws
Skills
Damage Resistances
Damage Immunities
Condition Immunities
Senses darkvision 60 ft., passive Perception 10
Languages --
Challenge 44934 (25 XP)

Keen Smell. The rat has advantage on Wisdom (Perception) checks that rely on smell.

Pack Tactics. The rat has advantage on an attack roll against a creature if at least one of the rat’s allies is within 5 feet of the creature and the ally isn’t incapacitated.

Actions

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) piercing damage.

Variant: Diseased Giant Rats

Some giant rats carry vile diseases that they spread with their bites. A diseased giant rat has a challenge rating of 1/8 (25 XP) and the following action instead of its normal bite attack.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) piercing damage. If the target is a creature, it must succeed on a DC 10 Constitution saving throw or contract a disease. Until the disease is cured, the target can’t regain hit points except by magical means, and the target’s hit point maximum decreases by 3 (1d6) every 24 hours. If the target’s hit point maximum drops to 0 as a result of this disease, the target dies.

Large beast, unaligned

Armor Class 12 (natural armor)
Hit Points 19 (3d10 + 3)
Speed 30 ft., climb 30 ft.

STR	DEX	CON	INT	WIS	CHA
15 (+2)	12 (+1)	13 (+1)	2 (-4)	10 (+0)	5 (-3)

Saving Throws
Skills
Damage Resistances
Damage Immunities
Condition Immunities
Senses darkvision 30 ft., passive Perception 10
Languages --
Challenge 44930 (50 XP)

Actions

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) piercing damage. A giant lizard can be ridden or used as a draft animal. Lizardfolk also keep them as pets, and subterranean giant lizards are used as mounts and pack animals by drow, duergar, and others.

Large beast, unaligned

Armor Class 11
Hit Points 39 (6d10 + 6)
Speed 20 ft., swim 40 ft.

STR	DEX	CON	INT	WIS	CHA
15 (+2)	13 (+1)	13 (+1)	2 (-4)	10 (+0)	3 (-4)

Saving Throws
Skills
Damage Resistances
Damage Immunities
Condition Immunities
Senses darkvision 30 ft., passive Perception 10
Languages --
Challenge 1 (200 XP)

Amphibious. The toad can breathe air and water.

Standing Leap. The toad’s long jump is up to 20 feet and its high jump is up to 10 feet, with or without a running start.

Actions

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (1d10 + 2) piercing damage plus 5 (1d10) poison damage, and the target is grappled (escape DC 13). Until this grapple ends, the target is restrained, and the toad can’t bite another target.

Swallow. The toad makes one bite attack against a Medium or smaller target it is grappling. If the attack hits, the target is swallowed, and the grapple ends. The swallowed target is blinded and restrained, it has total cover against attacks and other effects outside the toad, and it takes 10 (3d6) acid damage at the start of each of the toad’s turns. The toad can have only one target swallowed at a time. If the toad dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 feet of movement, exiting prone.

Large beast, unaligned

Armor Class 14 (natural armor)
Hit Points 26 (4d10 + 4)
Speed 30 ft., climb 30 ft.

STR	DEX	CON	INT	WIS	CHA
14 (+2)	16 (+3)	12 (+1)	2 (-4)	11 (+0)	4 (-3)

Saving Throws
Skills Stealth +7
Damage Resistances
Damage Immunities
Condition Immunities
Senses blindsight 10 ft., darkvision 60 ft., passive Perception 10
Languages --
Challenge 1 (200 XP)

Spider Climb. The spider can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Web Sense. While in contact with a web, the spider knows the exact location of any other creature in contact with the same web.

Web Walker. The spider ignores movement restrictions caused by webbing.

Actions

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 7 (1d8 + 3) piercing damage, and the target must make a DC 11 Constitution saving throw, taking 9 (2d8) poison damage on a failed save, or half as much damage on a successful one. If the poison damage reduces the target to 0 hit points, the target is stable but poisoned for 1 hour, even after regaining hit points, and is paralyzed while poisoned in this way.

Web (Recharge 5–6). Ranged Weapon Attack: +5 to hit, range 30/60 ft., one creature. Hit: The target is restrained by webbing. As an action, the restrained target can make a DC 12 Strength check, bursting the webbing on a success. The webbing can also be attacked and destroyed (AC 10; hp 5; vulnerability to fire damage; immunity to bludgeoning, poison, and psychic damage). To snare its prey, a giant spider spins elaborate webs or shoots sticky strands of webbing from its abdomen. Giant spiders are most commonly found underground, making their lairs on ceilings or in dark, web-filled crevices. Such lairs are often festooned with web cocoons holding past victims.

Huge beast, unaligned

Armor Class 13 (natural armor)
Hit Points 126 (11d12 + 55)
Speed 0 ft., swim 50 ft.

STR	DEX	CON	INT	WIS	CHA
23 (+6)	11 (+0)	21 (+5)	1 (-5)	10 (+0)	5 (-3)

Saving Throws
Skills Perception +3
Damage Resistances
Damage Immunities
Condition Immunities
Senses blindsight 60 ft., passive Perception 13
Languages --
Challenge 5 (1800 XP)

Blood Frenzy. The shark has advantage on melee attack rolls against any creature that doesn’t have all its hit points.

Water Breathing. The shark can breathe only underwater.

Actions

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 22 (3d10 + 6) piercing damage. A giant shark is 30 feet long and normally found in deep oceans. Utterly fearless, it preys on anything that crosses its path, including whales and ships.

Large beast, unaligned

Armor Class 13 (natural armor)
Hit Points 16 (3d10)
Speed 0 ft., swim 40 ft.

STR	DEX	CON	INT	WIS	CHA
12 (+1)	15 (+2)	11 (+0)	2 (-4)	12 (+1)	5 (-3)

Saving Throws
Skills
Damage Resistances
Damage Immunities
Condition Immunities
Senses passive Perception 11
Languages --
Challenge 44928 (100 XP)

Charge. If the sea horse moves at least 20 feet straight toward a target and then hits it with a ram attack on the same turn, the target takes an extra 7 (2d6) bludgeoning damage. It the target is a creature, it must succeed on a DC 11 Strength saving throw or be knocked prone.

Water Breathing. The sea horse can breathe only underwater.

Actions

Ram. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage. Like their smaller kin, giant sea horses are shy, colorful fish with elongated bodies and curled tails. Aquatic elves train them as mounts.

Large beast, unaligned

Armor Class 15 (natural armor)
Hit Points 52 (7d10 + 14)
Speed 40 ft.

STR	DEX	CON	INT	WIS	CHA
15 (+2)	13 (+1)	15 (+2)	1 (-5)	9 (-1)	3 (-4)

Saving Throws
Skills
Damage Resistances
Damage Immunities
Condition Immunities
Senses blindsight 60 ft., passive Perception 9
Languages --
Challenge 3 (700 XP)

Actions

Multiattack. The scorpion makes three attacks: two with its claws and one with its sting.

Claw. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) bludgeoning damage, and the target is grappled (escape DC 12). The scorpion has two claws, each of which can grapple only one target.

Sting. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 7 (1d10 + 2) piercing damage, and the target must make a DC 12 Constitution saving throw, taking 22 (4d10) poison damage on a failed save, or half as much damage on a successful one.

Medium aberration, neutral

Armor Class 9
Hit Points 67 (9d8 + 27)
Speed 10 ft., swim 10 ft.

STR	DEX	CON	INT	WIS	CHA
10 (+0)	8 (-1)	16 (+3)	3 (-4)	10 (+0)	6 (-2)

Saving Throws 
Skills 
Damage Resistances 
Damage Immunities 
Condition Immunities prone
Senses darkvision 60 ft., passive Perception 10
Languages --
Challenge 2 (450 XP)

Aberrant Ground. The ground in a 10-foot radius around the mouther is doughlike difficult terrain. Each creature that starts its turn in that area must succeed on a DC 10 Strength saving throw or have its speed reduced to 0 until the start of its next turn.

Gibbering. The mouther babbles incoherently while it can see any creature and isn’t incapacitated. Each creature that starts its turn within 20 feet of the mouther and can hear the gibbering must succeed on a DC 10 Wisdom saving throw. On a failure, the creature can’t take reactions until the start of its next turn and rolls a d8 to determine what it does during its turn. On a 1 to 4, the creature does nothing. On a 5 or 6, the creature takes no action or bonus action and uses all its movement to move in a randomly determined direction. On a 7 or 8, the creature makes a melee attack against a randomly determined creature within its reach or does nothing if it can’t make such an attack.

Actions

Multiattack. The gibbering mouther makes one bite attack and, if it can, uses its Blinding Spittle.

Bites. Melee Weapon Attack: +2 to hit, reach 5 ft., one creature. Hit: 17 (5d6) piercing damage. If the target is Medium or smaller, it must succeed on a DC 10 Strength saving throw or be knocked prone. If the target is killed by this damage, it is absorbed into the mouther.

Blinding Spittle (Recharge 5–6). The mouther spits a chemical glob at a point it can see within 15 feet of it. The glob explodes in a blinding flash of light on impact. Each creature within 5 feet of the flash must succeed on a DC 13 Dexterity saving throw or be blinded until the end of the mouther’s next turn.