"You will need a base of operation, a secret stronghold."
"I know the perfect place."-Nova Terron and Emerald, in the end of "How to Train a Mysticon."
The Stronghold is where the second generation of Mysticons, as well as Malvaron and Doug Hadderstorm, operate their moves and objectives the save the realm and its people from any evil. It is an old abandoned castle underneath the present royal castle.
According to Emerald Goldenbraid, it is the "old, old castle", as the stronghold was the castle that got destroyed by an earthquake, so they built a castle on top of it before building a castle on top of that one. When Nova Terron tells the Mysticons to have a base of operations, Emerald suggests that place be "the Old, Old Palace".
- Nova Terron ("The Astromancer Job")
- Proxima ("Star-Crossed Sisters" & "Eternal Starshine of the Mage's Mind")
- Geraldine Yaga (Twin Stars Unite")
- Tazma (against her will; "Save the Date")
- Gawayne ("The Lost Scepter")
- Citrine Goldenbraid ("Total Eclipse of the Golden Heart")
- Stormy ("The Last Dragon")
- Kitty Boon ("Game of Phones")
- Kasey Boon ("Game of Phones")
- Deeva ("The Foz Who Saved Lotus Night" and "Eternal Starshine of the Mage's Mind")
- Kymraw ("The Foz Who Saved Lotus Night")
- Eartha ("Heart of Stone" and "Eternal Starshine of the Mage's Mind")
- Mallory, Kasha and Willa ("Eternal Starshine of the Mage's Mind")
Those Who Not Yet Visited
- Queen Goodfey
- King Darius
- Malachite Goldenbraid
- Halite and Ferrus Goldenbraid
- Serena Snakecharmer
- Barnabas Dinglelott
- Felix Castle
- Vanity Castle
The stronghold has bedrooms for all the Mysticons, as well as a living room area where they make plans and hang out, either by talking or playing video games. That is also where they store the codex pieces.There is also a lab full of spellbooks, mystical charms and talismans and potions, as shown in A Girl and Her Gumlump.
- How to Train a Mysticon (debut)
- The Coronation
- The Mysticon Kid
- An Eye for an Eye
- Scourge of the Seven Skies
- Lost and Found
- The Astromancer Job
- A Walk in the Park
- A Girl and Her Gumlump
- Skies of Fire
- Save the Date!
- Happily Never After
- The Lost Scepter
- Total Eclipse of the Golden Heart
- The Last Dragon
- Game of Phones
- The Foz Who Saved Lotus Night
- Heart of Stone
- The Princess and the Pirate
- Monster Hunt
- Eternal Starshine of the Mage's Mind
- Age of Dragons (final appearance)
The Stronghold in Printed Media
- It was officially called "the Stronghold" by Malvaron in "Scourge of the Seven Skies" and "the Mysticon Stronghold" by Mallory.
- Nova Terron is shown to know where the stronghold is, as he went there in "The Astromancer Job".
- Geraldine Yaga also seems to know where it is, as she opened an orange portal directly to it in "Twin Stars Unite."
- Proxima was taken to the Stronghold, though blindfolded, by Arkayna in "Star-Crossed Sisters"
- For some reason, every villain has been able to find where it is and break in with ease.
- Gawayne, naturally, thinks it is "hex-tag: sad" and "boring."
- After being restored to living flesh and blood, Queen Goodfey nor King Darius visit the base of operations where their fraternal twin daughters and stepdaughters constantly meet to plan their next battle stagey as Mysticons.
- For some reason, every villain seems to know exactly where it is and how to sneak in; such as Kymraw, Deeva and the Vexicons.
- Its last appearance in the show, was when Malvaron and Doug were playing video games.