Design + DM Diaries (and Bonus Trap!)

Hey folks! Hannah here—I ran a really fun D&D session earlier this week, and since I decided to modify one of the traps in Horizons 2 for use in my game, I wanted to share the result with all of you and explain the process of customizing the trap, and some stat blocks, to fit my needs.

Since the characters were looking for an item in an icy environment, I decided to adapt the Melting Treasure trap into a Frozen Treasure Chest trap.

 (You can download this trap as a PDF attached to this post.)

One of our goals with Horizons is to create material that’s easily usable as-is (saving GM prep time and stress, as always!) but also fun and easy to adapt to fit your game—whether that’s changing up the details of a trap, like this one, or converting it to use with another system entirely, as some folks in our Discord have already done. Especially if you’re newer to GMing, I hope this is a useful example of adjusting published content that gives you extra confidence to do it yourself.

Read on to learn about the choices behind the trap adaptions (tradaptions?), take a peek at my session prep notes, and find out how it all went in game!

Adjusting the Trap

I could have chosen any trap to rework for the cold environment—a Summoning Book that summons Ice Mephits instead of Imps, or a Crushing Room whose walls are made of ice and can be melted with sufficient application of heat—but I liked the imagery of having characters restrained by ice instead of melted metal. Plus, one of the PCs has an ability that lets them free a Restrained creature with a touch, so I thought it’d give them a moment to shine.

I made the following changes to turn the Melting Treasure trap into this Frozen Treasure Chest version:

• Changed the damage type from Fire to Cold (duh). Characters are less likely to have Resistance to Cold damage, but that isn’t a big enough deal to change the amount of damage from the trap. If you want the trap to deal less damage, you could lower it to d8s rather than d10s, though.

• Changed the school of magic from Transmutation to Evocation; instead of melting and re-solidifying material, this trap imbues the chest with frosty energy and then explodes outward in a blast of ice.

• Created a new list of creatures to use alongside the trap. Immunity to Cold damage and/or the Restrained condition became more important thematically than mechanically, since the enemies could be hidden inside the trapped object or otherwise freed by the explosion instead of being affected by it, but I liked the list of creatures I came up with by considering those Immunities.

Prepping and Running the Session

This was a game with three level 6 characters (one player couldn’t make it): a wizard, a paladin, and a witch (using the Worlds Beyond Number Witch class).

I ended up putting a modified Black Pudding inside the chest because I liked the idea of an enemy literally oozing out, but I made some quick adjustments to the stat block. The following is copied straight from my notes: 

Shadow ooze (in chest)

• Deals necrotic instead of acid damage

• Instead of reducing weapon and armor effectiveness, attempts to subsume a nonmagical weapon or piece of armor on a critical hit? (slurp)

• Splits when subjected to radiant or slashing damage

I made the first two changes partly because I was worried tracking the Black Pudding’s usual debuffs to nonmagical weapons and armor would be a frustrating player experience (I try to save my “mean GM” moves for things other than making equipment worse) and because I needed to explain why this ooze was chilling—no pun intended—inside of the trapped chest instead of dissolving both the chest and and the quest items I wanted to place inside it. 

By that point, I’d decided to call the creature a Shadow Ooze and I figured it would be fun to have it split when it takes Radiant damage (instead of the usual Lightning damage), especially since there’s a paladin in the party.

Then I threw some Poltergeists in as tormented spirits who were disturbed by the explosion (conveniently Resistant to Cold damage and Immune to the Restrained condition, though I placed them outside of the blast radius regardless). The plan was for these enemies to transition into a second phase with the Specter stat block after being reduced to 0 HP, but we ended up running out of time in the session so I just let the party defeat them.

I also had an abstract countdown going on with the time until sunset based on the party’s successes with various Survival and Investigation checks to navigate to this location and find the chest in the first place. That might have affected things mechanically because Specters have Sunlight Sensitivity, but mostly it was a way to introduce some narrative time pressure and the threat that things might get worse if they didn’t move quickly.

Notable game moments included: 

• The wizard cast Elemental Weapon on the paladin’s whip, turning it into a badass fire whip. The paladin ended up splitting the ooze with a Divine Smite critical hit that dealt a buttload of Radiant and Fire damage, and then taking out each of the smaller oozes on the next round! (When an ooze splits, do both the new oozes have the same conditions? I ruled that they do.)

• The witch used her Retributive Curse when one of the spirits threw a barrel at her, negating its Invisibility and granting Advantage on attacks against it via Vengeful Gleam (essentially a Faerie Fire curse) that allowed the wizard to obliterate it with Scorching Ray. 

• The witch also ended up getting the kill on the final spirit with Spellwarping Curse when it tried—and failed—to telekinetically shove her. (We're still testing the class, and this was good playtest data, actually.)

And the Frozen Treasure Chest trap? Well … there’s a reason the Horizons table of contents has a combined “Traps & Puzzles” tag. Between a good Intelligence (Arcana) check and a clever if not quite rules-as-written use of the Identify spell, the party was able to deduce the mechanics of the trap. They then triggered it from outside the blast radius with Knock, avoiding the effects entirely.

Would it have been fun if they’d just touched the trapped chest and I could have narrated them being literally frozen to the walls? Sure. But honestly, it was just as fulfilling to have them solve it as a puzzle. It was also an extra challenge opportunity for me to pivot and incentivize them to open the chest even once they knew it was a trap; I let them learn the list of creatures who could safely touch it, which included the long-ago elven witch queen they were investigating.

How would you adapt this trap for your games? What have your players gotten up to while trying to circumvent traps or unwittingly stumbling into them? Let me know in the comments or our Discord server!

Until next time,

Hannah, Editor-in-Chief

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