Here is a list of 20 one-time-use special attacks or actions that can be used for any monster. Especially the low CR monsters. I like to make sure at least one baddie stands out in an encounter and this list is always a good start.
Roll a d20 or choose your own. Once per day or once per short/long rest.
- Multiattack. The monster makes two attacks.
- Perception Check. The monster makes a Wisdom (Perception) check.
- Misty Step. The monster can teleport up to 30 feet to an unoccupied space they can see.
- Parry. The monster can use a reaction to add 2 to its AC, turning a successful attack into a failed one.
- Cantrip. The monster casts a cantrip.
- Disengage. The monster can take the disengage action as a bonus action.
- Explode. The monster destroys itself in a fiery blast. Each creature within 10 ft. must make a DC 10 + 1/2(CR) Dexterity saving throw. A target takes 2d10 fire damage on a failed save, or half as much damage on a successful one.
- Paralyze. On a successful attack, the target must succeed on a DC 10 + 1/2(CR) Constitution saving throw or be paralyzed until the end of its next turn.
- Charge. If the monster moves at least 10 feet in a straight line right before attacking a creature and hits with the attack, that target must succeed on a DC 10 + 1/2(CR) Strength saving throw or be knocked prone.
- Invisible. As a bonus action, the monster can magically turn invisible until the start of its next turn or until it attacks, makes a damage roll, or forces someone to make a saving throw.
- Inspiration. The monster can use a bonus action to choose one creature other than itself within 60 feet of you who can hear you. That creature gains one Inspiration die, a d6.
- One Luck Point. Whenever the monster makes an attack roll, ability check, or saving throw, you can spend one luck point to roll an additional d20.
- Help Action. The monster can aid a friendly creature in attacking a creature within 5 feet of you and the first attack roll is made with advantage.
- Apply Poison. As a bonus action, the monster licks its weapon adding poisoned saliva. On a successful attack, the target takes an extra 2d6 poison damage.
- Frighten. Any creature within 10 ft. must make a DC 10 + 1/2(CR)Wisdom saving throw or be frightened for 1 minute.
- Charm. Any creature within 10 ft. must make a DC 10 + 1/2(CR) Wisdom saving throw or be charmed for 1 minute.
- Trip. On a successful attack, the target must succeed on a DC 10 + 1/2(CR) Strength saving throw or be knocked prone.
- Grapple. On a successful unarmed strike, the target is Grappled, and the grapple’s escape DC 10 + 1/2(CR).
- Sneak Attack. Deal an extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll or another enemy of the target is within 5 feet of it.
- Wand of Magic Missile. The creature uses the last charge of a Wand of Magic Missiles.
Got any abilities that should be added to the list? Let me know in the comments below!