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- I Cast...Brainstorm issue 25!
I Cast...Brainstorm issue 25!
A weekly newsletter of ideas and advice for D&D Dungeon Masters, players, and fans
Dave Palmer
September 26th, 2025
This week — A completely un-playtested monster and spell, ‘cause why not? We’re Brainstorming!
Thanks for reading I Cast…Brainstorm!, a weekly newsletter with ideas and advice to help make DM-ing and playing D&D (and other TTRPGs) easier and more fun.
You can say hello, share feedback, and let me know what you’d like to see in the newsletter at [email protected].
And please share our link with your friends and fellow gamers, so they can join us, too. https://icastbrainstorm.beehiiv.com/
Let’s brainstorm some fun!
In this issue...
What a fun week of games!
My Tuesday night Rime game felt much more fun and challenging, and after a month off I DM-ed at the bar this week. The two games have such different energy, and I love them both. The Tuesday crew are great role-players, and the game has a ton of lore, and is very character-driven, detailed and rules-oriented. And the bar game? That’s just a loud, raucous, silly burst of energy where pretty much anything goes.
The question I’m mulling over — is there a way to combine both of those experiences, using the best qualities of both, to create the perfect session?
Until I figure that out, I hope you like the un-playtested and (I think) fun ideas below. If you try them out, I’d love to know how they played, and what you think about ‘em. Happy gaming!
A New Monster for Urban Environments
I love the feel of this monster, and can’t wait to try it in one of my games. If you try it, beware the Consume Head attack! Its nasty.
Cloaked Mantises can be found in dark forests, though they prefer to infest abandoned buildings in urban areas. Nocturnal hunters, cloaked mantises cover themselves with their hardened carapaces, and stand upright, which in dim light makes them easy to misidentify as tall, thin humanoids wearing long cloaks and feathered hats. An infestation of cloaked mantises will grow in number to fill the nest, but they usually hunt alone or in small groups, relying on stealth and they’re flying ability to make an easy kill and then escape.
Cloaked Mantis
Medium Monstrosity, Neutral
AC 17, natural armor (AC 15 when flying)
HP 55 (10d8 + 10)
Speed 20’, fly 40’
Initiative +3
STR 17 (+3), save +3
DEX 16 (+3), save +3
CON 12 (+1), save +1
INT 6 (-2), save -2
WIS 10 (+0), save +0
CHA 6 (-2), save -2
Skills — Perception +4, Stealth +5
Damage Resistances — Poison
Damage Immunities — None
Condition Immunities — Paralyzed
Gear — None
Senses — Darkvision 60’, Passive Perception 14
Languages — None
Habitat — Forest, Urban
Treasure — None
CR 3 (XP 700) Proficiency Bonus +2
Features
Hardened Carapace
A cloaked mantis can cover itself with its hardened carapace to gain a +2 bonus to its AC. To fly, it must open the carapace, making it more vulnerable to attacks.
Actions
Multiattack
The cloaked mantis makes two attacks, but can only make one Bite or Consume Head attack per turn.
Bite
Melee Weapon Attack: +5 to hit, reach 5 ft., target: one creature
Hit: 7 (1d8 + 3) piercing damage, and the target must succeed on a DC 11 Constitution saving throw or be poisoned for 1 minute. If the saving throw fails by 5 or more, the target is also paralyzed while poisoned in this way. The poisoned target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Claw
Melee Weapon Attack: +5 to hit, reach 5 ft., target: one creature
Hit: 8 (1d10 + 3) slashing damage. If the target is a Large or smaller creature, the cloaked mantis can choose to grapple the target, (escape DC 13). Until this grapple ends, the target is restrained. The cloaked mantis can only grapple one creature at a time, and can only make 1 claw attack per turn while grappling.
Consume Head
Melee Weapon Attack: +5 to hit, reach 5 ft., target: one paralyzed creature grappled by the cloaked mantis
Hit: The target takes 27 (5d10) piercing damage. If this damage reduces the target to 0 hit points, (and the target has a head), the cloaked mantis instantly kills the target by consuming its head.
A New Control Spell
It feels like this spell may be very versatile — it could create a cushion from falling damage, or a barricade from ranged attacks, or it could make a swarm of flying creatures stop in their tracks. If you try it out, please let me know how it plays!
Coagulate Ether
Concentration
Level 3rd
Casting Time 1 Action
Range/Area 120 ft., 30’ cube
Components V, S
Duration Concentration, up to 1 Minute
School Transmutation
Attack/Save STR Save
Damage/Effect Control
You cause the air in a 30’ cube within range to coagulate and thicken, causing any creatures inside to succeed on a Strength saving throw or become trapped in place and suffocate. The coagulated air does not affect vision at all, but hearing and smell are suppressed.
Any creature trapped in the coagulated air has a speed is 0’, is incapacitated, cannot move, speak or breathe, and any spell-casting that relies on speech or movement is impossible. A trapped creature makes a Strength saving throw at the start of each of its turns, and on a successful save, it can breathe, speak and move normally, although a creature’s speed through the coagulated air is only 5’.
Weapon attacks cannot pass through the thickened air, and ranged magic is suppressed by it, (moving through the thickened air at a speed of 5’ per round, and decreasing the radius of any blast or emanation by 50%). Creatures trapped at the edge of the 30’ cube can be attacked normally.
Brainstorming Links
You probably already know about the folks below, who are real inspirations to me, but if not, do yourself a favor and check them out.
The Arcane Library — masterpiece adventures, and Shadowdark, too!
https://www.thearcanelibrary.com
The Angry DM — so angry….so many great ideas….
https://theangrygm.com/
DMDave — on point analysis of D&D rules, and a ton of fun ideas
https://bsky.app/profile/dmdave.bsky.social
RPGBot — whip smart critique and explanations of 5e rules
https://rpgbot.net/
Sly Flourish — a DM’s best friend who is also a better DM
https://www.slyflourish.com/
Treantmonk — years of helpful advice and clever ideas
https://www.youtube.com/@TreantmonksTemple
If you like I Cast…Brainstorm!, you might also like these amazing newsletters with more great ideas, advice and news about RPGs.
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What I’m DM-ing
A high-level campaign via Roll20 using 2014 5th edition rules (currently 12th level)
A weekly Rime of the Frostmaiden campaign, in-person, with 2024 5th edition rules
A series of one-shots in a bi-weekly game at a bar in LA. If you’re interested in joining in, invites are sent via the Partiful app, and you can sign up at Ye Rustic Inn — 1831 Hillhurst Ave, Los Angeles, California.
Two different campaigns with my kids, (Rime and Storm Kings Thunder) when schedules align
What I’m Playing
Vecna: Eve of Ruin as Clybb Thistlebridge, a 9th level Halfling great-weapon Fighter
If you play Hearthstone, find me at BigKahuna (#1802)
Also, I just purchased all the gold-box D&D CRPGs via Humble Bundle, so I guess I’ll do a deep dive into those soon!
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If you have an online store that sells D&D or TTRPG themed things, let me know — I’d love to add it here.
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What Do You Think?
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The original ideas in this issue of I Cast….Brainstorm! are covered under the Creative Commons BY-SA license — all content is free to use (including commercially) and change, with proper attribution.
You can read about the license here: https://creativecommons.org/licenses/by-sa/4.0/deed.en
