The micro castle/pirate collaboration standard was introduced for Brickworld 2015 as a way to allow fans of the castle and pirate themes get involved on any level of commitment. Based on the fan-created microscale standard, it specifies an octagonal base to create the appearance of a more natural terrain.
A module consists of one or more contiguous 10x10 octagonal plates with a 4x4 plate appended to the left side. The actual octagonal plate [[element] is not required so long as the end result is the same profile. The four of 4x4 corner plate cut plus some filler plates work for this. Baseplate total height is 1 brick + 1 plate, or four plates. The standard defines microscale as any scale smaller than minifig scale.
Here are the rules as posted on Brickworld
1. Each module is made from a 10X10 octagon + a 4X4 square. 2. The 4X4 square area goes on the left. 3. Modules are 1 brick + 1 plate high. 4. You can build things that are larger than what will fit on 1 module. Just make sure that you connect your adjecent modules together and build across them without going over the edges. 5. There is no limit to the number of modules you can bring. 6. The display coordinator is responsible for bringing/building a border around the perimeter to keep the modules from shifting around.