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Improvise 5e Monster Abilities
by Mike on 12 September 2022
From this moment forward, consider yourself given the freedom to change monsters as you see fit for the fun of your game.
You, of course, had this freedom all along but I suspect some DMs feel like modifying monster stat blocks, particularly in the middle of a session, is "cheating".
It's not.
It takes experience to know what to add to a monster to make it interesting in the moment. It's not something a new DM can likely do without breaking something. But eventually we run enough monsters to have some back-pocket special abilities we can add to a monster. Maybe it's as simple as an extra attack. Maybe it's some elemental damage. Maybe it's a spell effect. I loved adding spell effects to armored flesh golems in my Tomb of Annihilation game. Every flesh golem was a unique horror.
When should we consider such changes? Sometimes we want a monster to act more appropriately dangerous mechanically to fit its story. Sometimes we want to change up a monster the players are already used to seeing. Sometimes we want to change a boring encounter into a nail-biter. Sometimes we want to make a monster unique.
What are some simple ways you can modify existing stat blocks? Here are a few. For DCs, make the DC 12 + 1/2 the CR of the monster.
- Strength save or be knocked prone.
- Strength save or be pushed back.
- Super-fast movement that doesn't provoke opportunity attacks.
- A ranged attack if they don't have one (use one of its melee attack stats but reflavor it).
- An extra attack if they could use another.
- Pack tactics.
- A whirlwind or ground stomp attack that attacks adjacent enemies.
- Constitution save or be poisoned until the end of the monster's next turn.
- Elemental damage based on the monster's story to its weapon attack. Consider 3 (1d6) damage up to CR 5, 7 (2d6) at CR 5 to 10, 14 (4d6) at CR 11 to 16, 28 (8d6) at CR 17+.
- A fire shield like damaging shield. Consider 4 (1d8) damage up to CR 4, 9 (2d8) at CR 5 to 10, 13 (3d8) at CR 11 to 16, 18 (4d8) at CR 17+. Flavor the damage based on the monster's story.
- A spirit guardians like damage aura in which those who start within or enter it take damage. Consider 9 (2d8) damage up to CR 4, 13 (3d8) at CR 5 to 10, 18 (4d8) at CR 11 to 16, 27 (6d8) at CR 17+. Flavor the damage based on the monster's story.
Of course, these new abilities should make sense for the monster and for the situation. Flavor these abilities in the fiction of the game. Telegraph them so players can see the monster's doing something different. Show the fire giant who sets its blade ablaze. Describe flails dripping with acid or assassins surrounded by the screaming spirits of their slain victims. Show the vampiric-touched ghoul who moves faster than the eye can see. Wrap your mechanical changes in interesting flavorful descriptions.
Add these abilities when they make combat more interesting or tell a more interesting story. Don't add them to punish players, particularly to punish players for good ideas or good luck. And don't go overboard. One modification per monster is often enough. Bosses might have lots of things to do but a normal monster might just have a kicker effect on its normal attack.
Become comfortable enough with the mechanics of 5e to be confident adding these sorts of changes. Once you start to get comfortable, once you see your players enjoying the change in tactics and mechanics, you'll know you're in the right place.
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