# Brennan Lee Mulligan
**Brennan Lee Mulligan** is an American writer, actor, and game master best known as the creator, executive producer, and Dungeon Master of *Dimension 20*, the tabletop role-playing game show produced by CollegeHumor's streaming service Dropout.[1](https://brennanleemulligan.com/brennans-bio/) He is also a co-founder and game master of the actual-play podcast *Worlds Beyond Number*[2](https://ucbcomedy.com/people/brennan-lee-mulligan/) and, from 2025, the game master of [Critical Role](https://www.edgepedia.org/critical-role)'s fourth core campaign.[3](https://au.variety.com/2025/digital/news/critical-role-brennan-lee-mulligan-campaign-4-26019/)
| Key fact | Detail |
|---|---|
| Signature role | Executive producer, writer, and Game Master of *Dimension 20* on Dropout[1](https://brennanleemulligan.com/brennans-bio/) |
| Webby Award | Wrote and starred in the CollegeHumor sketch *Tide CEO*, which won a 2019 Webby Award and received over eight million views[1](https://brennanleemulligan.com/brennans-bio/) |
| Comics | Author and co-creator (with Lee Knox Ostertag) of the webcomic and graphic novel series *Strong Female Protagonist*, named an Autostraddle Favorite and on io9's list of Best New and Short Webcomics[1](https://brennanleemulligan.com/brennans-bio/) • [4](https://dimension20.wiki.gg/wiki/Brennan_Lee_Mulligan) |
| Critical Role | Dungeon Master for *Exandria Unlimited: Calamity*, *Downfall*, and *Exandria Unlimited: Divergence*; Game Master of Campaign IV, which began in October 2025[5](https://www.imdb.com/name/nm3293702/) • [4](https://dimension20.wiki.gg/wiki/Brennan_Lee_Mulligan) |
| Podcast | Co-founder and GM of *Worlds Beyond Number*, supported by over 20,000 Patreon subscribers as of February 2023[2](https://ucbcomedy.com/people/brennan-lee-mulligan/) • [6](https://www.dndbeyond.com/posts/1454-interview-brennan-lee-mulligan-on-worlds-beyond?msockid=166c330b317d6de80acc2574301b6c94&page=2) |
| Improv background | Taught and performed for years at the Upright Citizens Brigade Theater on both coasts; member of the UCB Touring Company and Harold Night[1](https://brennanleemulligan.com/brennans-bio/) |
| Voice work | Voiced Tyler Locke in Audible's 14-hour, Audie-nominated occult thriller *Locke & Key*[1](https://brennanleemulligan.com/brennans-bio/) |
## Dimension 20
*Dimension 20* is an actual-play series in which a table of comedians and performers tell stories through tabletop role-playing games, usually using a [Dungeons & Dragons](https://www.edgepedia.org/dungeons-and-dragons) ruleset, with Mulligan as the regular Dungeon Master.[7](https://www.thewrap.com/dimension-20-brennan-lee-mulligan-interview-battle-at-the-bowl/) • [8](https://time.com/7020897/dungeons-and-dragons-live-performances/) By September 2024 the series had run 22 seasons, with themes ranging from a fantasy high school in the show's first season, *Fantasy High*, to a court of Regency-era archfey, and a live show at [Madison Square Garden](https://www.edgepedia.org/madison-square-garden), Gauntlet at the Garden, had been announced.[8](https://time.com/7020897/dungeons-and-dragons-live-performances/)
The recurring main cast, known as the Intrepid Heroes, consists of Siobhan Thompson, Emily Axford, Zac Oyama, Brian Murphy, Lou Wilson, and [Ally Beardsley](https://www.edgepedia.org/ally-beardsley). Before pitching the show, Mulligan had already been running games for five of the six; Beardsley, who had never played Dungeons & Dragons, learned the game on screen as Kristen Applebees in *Fantasy High*.[8](https://time.com/7020897/dungeons-and-dragons-live-performances/) In 2023 the series released *Dungeons and Drag Queens*, featuring royalty from *RuPaul's Drag Race*.[8](https://time.com/7020897/dungeons-and-dragons-live-performances/) Mulligan has appeared in more seasons of the show than any other cast member, as either player or Dungeon Master, and hosts the Dropout vodcast *The Adventuring Academy*, where he discusses aspects of playing Dungeons & Dragons with rotating guests.[4](https://dimension20.wiki.gg/wiki/Brennan_Lee_Mulligan) • [1](https://brennanleemulligan.com/brennans-bio/)
In 2025, Variety reported that Mulligan had signed a new three-year deal with Dropout while taking on the Game Master role for Critical Role's next core campaign.[3](https://au.variety.com/2025/digital/news/critical-role-brennan-lee-mulligan-campaign-4-26019/) Campaign IV, which began in October 2025, features a 13-player cast split into three rotating groups in a West Marches (A campaign format with rotating players exploring an open, shared game world) structure, with [Matthew Mercer](https://www.edgepedia.org/matthew-mercer), Critical Role's usual Dungeon Master, playing as a character.[9](https://www.pcgamer.com/movies-tv/critical-role-campaign-4s-first-13-player-ensemble-episode-is-chaotic-messy-and-gripping-d-and-d-and-i-feel-like-ive-just-seen-a-magician-pull-a-fully-formed-rabbit-out-of-a-hat/)
## Other game master work
Outside Dropout, Mulligan has game-mastered campaigns for Critical Role, including *Exandria Unlimited: Calamity*, *Downfall*, and *Exandria Unlimited: Divergence*.[5](https://www.imdb.com/name/nm3293702/) • [4](https://dimension20.wiki.gg/wiki/Brennan_Lee_Mulligan) His engagement with *Exandria Unlimited: Calamity* was received as a crossover event and as a demonstration of his standing in the actual-play community.[10](https://theses.gla.ac.uk/84805/1/2024FrenchPhD.pdf)
*Worlds Beyond Number*, which he co-founded with Aabria Iyengar, Erika Ishii, and Lou Wilson, launched its first campaign, *The Wizard, the Witch, and the Wild One*, on March 1, 2023. The podcast was creator-owned and supported by over 20,000 Patreon subscribers as of February 2023.[6](https://www.dndbeyond.com/posts/1454-interview-brennan-lee-mulligan-on-worlds-beyond?msockid=166c330b317d6de80acc2574301b6c94&page=2)
## Early exposure to role-playing and writing career
Mulligan was introduced to tabletop role-playing games by his mother, the playwright and writer Elaine Lee, who authored the science fiction play and graphic novel series *Starstruck* and helped him find a gaming group and learn to play. He began running games for friends at age 10.[8](https://time.com/7020897/dungeons-and-dragons-live-performances/) • [4](https://dimension20.wiki.gg/wiki/Brennan_Lee_Mulligan) The *Starstruck* universe is the setting of the *Dimension 20* season *A Starstruck Odyssey*.[4](https://dimension20.wiki.gg/wiki/Brennan_Lee_Mulligan)
His background is in live role-playing and improv. He was a head storywriter for The Wayfinder Experience, a live-action role-playing camp in upstate New York where he wrote dozens of LARPs, a director and performer for Story Pirates, and a member of the UCB Touring Company and Harold Night.[1](https://brennanleemulligan.com/brennans-bio/) • [2](https://ucbcomedy.com/people/brennan-lee-mulligan/) He has described meetings, pre-production, and planning as the bulk of his working week, with one or two days set aside for writing.[11](https://www.pedestrian.tv/brennan-lee-mulligan-interview)
As a cast member of [CollegeHumor](https://www.edgepedia.org/collegehumor) he wrote and starred in *Tide CEO*, which won a 2019 Webby Award and received over eight million views. He also co-created *Strong Female Protagonist*, received an Excellence in Performance Award from the NY Fringe Festival for playing the lead in *…And Then She Dies at the End*, and has appeared on *Adam Ruins Everything* and in sketches for CollegeHumor, Funny Or Die, and Above Average.[1](https://brennanleemulligan.com/brennans-bio/)
## References
1. [Brennan's Bio, brennanleemulligan.com](https://brennanleemulligan.com/brennans-bio/)
2. [Brennan Lee Mulligan, Upright Citizens Brigade](https://ucbcomedy.com/people/brennan-lee-mulligan/)
3. [Critical Role Sets Brennan Lee Mulligan as Game Master for Next Core Campaign as He Signs New Three-Year Deal With Dropout, Variety](https://au.variety.com/2025/digital/news/critical-role-brennan-lee-mulligan-campaign-4-26019/)
4. [Brennan Lee Mulligan, Dimension 20 Wiki](https://dimension20.wiki.gg/wiki/Brennan_Lee_Mulligan)
5. [Brennan Lee Mulligan, IMDb](https://www.imdb.com/name/nm3293702/)
6. [Interview: Brennan Lee Mulligan on Worlds Beyond Number, D&D Beyond](https://www.dndbeyond.com/posts/1454-interview-brennan-lee-mulligan-on-worlds-beyond?msockid=166c330b317d6de80acc2574301b6c94&page=2)
7. [Dimension 20's Brennan Lee Mulligan's 2 Tricks for Juggling His Many Stories, TheWrap](https://www.thewrap.com/dimension-20-brennan-lee-mulligan-interview-battle-at-the-bowl/)
8. [Live Performances of Dungeons & Dragons Are Filling Stadiums and Going Mainstream, TIME](https://time.com/7020897/dungeons-and-dragons-live-performances/)
9. [Critical Role: Campaign 4's first 13-player ensemble episode, PC Gamer](https://www.pcgamer.com/movies-tv/critical-role-campaign-4s-first-13-player-ensemble-episode-is-chaotic-messy-and-gripping-d-and-d-and-i-feel-like-ive-just-seen-a-magician-pull-a-fully-formed-rabbit-out-of-a-hat/)
10. [A French PhD thesis on actual play, University of Glasgow](https://theses.gla.ac.uk/84805/1/2024FrenchPhD.pdf)
11. [Brennan Lee Mulligan Defines His "Height Of Human Achievement", PEDESTRIAN.TV](https://www.pedestrian.tv/brennan-lee-mulligan-interview)
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*Topic: Encyclopedia › Arts and culture › Screen and stage › Film and television › Screen people and creators › Screenwriters and television writers › Television writers*
*Initially written Sep 17, 2026 · Reviewed: Oct 25, 2026 · Edited: Oct 12, 2026; Oct 15, 2026; Oct 25, 2026 · Last review: Oct 25, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license