"castle" fails to load, see map test.
Kartotherian currently includes Maki 0.5.0, which is not the latest version of Maki icons documented on mapbox.com. Therefore, some icons, like the castle icon, are not available yet.
See the list of available icons at mw:Maps/Icons
This task was mentioned at Community-Wishlist-Survey-2017 (https://meta.wikimedia.org/wiki/2017_Community_Wishlist_Survey/Miscellaneous/Kartographer_improvements), which got the No.1 out of 214 proposals.