Duncan's Castle was built by Duncan in his Tekkit series so he had more room for his machines. It was his main base of operations. Later it was attacked by the Nagas from the holiday with Duncan, Kim, and Simon. It featured in the Duncan and Kim's Galacticraft series, Episode 38, where they find the old castle overrun with taint.
Duncan built the castle so he could build more machines and because he wanted to look more like a mad scientist. It took Duncan two episodes to complete the castle. From then on Duncan has added a cellar for beer and rum, a giant reinforced glass globe to house a nuclear reactor, a working gate to enter and exit the castle and he has dedicated each room to a different part of Tekkit. He has added a force-field to protect his castle from a possible attack from his nemesis Rythian. The castle has since been destroyed by a large pack of Naga.
At some point after being destroyed the Castle was moved into a different dimension and tainted with flux.
Around the 85th episode of Flux Buddies, due to Duncan and Kim finding out that someone else (namely Dr. Lalnable Hector) was using the castle as an experimentory lab and Duncan and Kim no longer having any use for the castle, they decided to launch Hypersonic and Nuclear Cluster missiles at the castle to destroy both the castle itself as well as the taint and flux around it in order to stop it spreading.
- Underground lab
- Wither Skeleton Spawner
- Computer room
- Matter creation
- Bone machine (EMC generator) (Most likely broken due to the upgrade to Yogscraft, though it has not been confirmed)
- Blaze rod machine (EMC generator) (Most likely broken due to the upgrade to Yogscraft, though it has not been confirmed)
- Diamond chest (as result of the EMC generators)
- Dark Matter creator (Most likely broken due to the upgrade to Yogscraft, though it has not been confirmed)
- Red Matter creator (Most likely broken due to the upgrade to Yogscraft, though it has not been confirmed)
- Sorting machine
- Portal to Secret Base
- Macerator/compressor/drop off chest (to be sorted)
- Power room
A second tower has been used to house the globe that has a nuclear reactor in it as well as create TNT minecarts as ammunition for the railgun.
The third tower has recently became the control tower for the railgun, housing wireless system connecting railgun to the computer.
The fourth tower is used by Kim as her house and her Mage's tower, called "Kim's Tower of Doom and That". This contains some very basic Industrialcraft machines and a Batbox to charge her jetpack.
During the Christmas 2012 Livestreams, Sips and Sjin took over for a day, accompanied by Duncan and Sparkles*, and played on the Yogscast Tekkit server. They built a large 'S' on the side of one of their buildings, which was coloured blue, orange and white, to symbolize Sips and Sjin's spacesuits. Sips, Sjin, Duncan and Sparkles* decided that when the donations reached £133,700, they would destroy Rythian's castle using the nuke placed underneath it by Duncan. Not surprisingly, Rythian didn't want Sips and Sjin to blow up his base, so he disabled the nuke, even though Ridgedog promised to load the server backup file afterwards, which would reset the destruction. To honour the fans that donated, Sips and Sjin decided to blow up the SipsCo. compound, followed by Duncan's Castle. SipsCo. was meant to be destroyed, but because of the anti-nuke measures on the server, they couldn't destroy it, but they managed to blow up Duncan's Castle and Rythian's base. After doing so, the server was reloaded to before the destruction of Duncan's Castle.
- Duncan has decorated his castle for Halloween with Jack O' Lanterns.
- Duncan then re-decorated for Christmas, adding a star, Christmas lights and turned his nuclear reactor into a giant Christmas pudding.
- Duncan can see Honeydew Inc. from his railgun, as long as his render distance is set to far. The object that was there before, a telescope, was used to symbolize Duncan's relationship with Honeydew Inc., as the telescope was pointed towards the Jaffa Factory.
- Duncan made a UFO to put in the hangar in his compound.