To finish up my mod, I built another custom mob goal, except this time for building. I noticed that the mob tended to get stuck a lot, so now whenever it gets stuck it will place blocks in a path to get out! It can also bridge to players from wherever they are, in straight, stair and tower forms. I spent a bit of time tweaking this system so that the building doesn’t interfere with the rest of the mob. I also added some particles to indicate when the entity is in each of its forms, with red being the final form color.