With the way realm permissions work, anyone given build rights to make border cairns for a realm also has rights to destroy these cairns. Everyone wants to be inside a realm for the buffs and cool chat, but it is unsafe for realm owners to give out build permissions to allow others to help. They might unknowingly give rights to someone with malicious intent, who would then destroy cairns rather than build. Building cairns is very time and resource intensive, but destroying them requires nothing but water and has no cool down at all. This means even if an army of strangers were recruited to expand a realm and only one turned out to be a treacherous saboteur, the one bad builder would be able to cause a huge amount of damage to realm coverage and cancel out the gains from all the others, meaning the only logical choice for realm owners is to simply not receive help from anyone in expanding a realm.
Many players I have run into are very invested in being claimed by one realm or another, and gladly offer up their time and resources in order to help themselves get claimed. However, they simply are not able to contribute anything because it is not worth the risk of give out building rights. A possible solution for realm owners is to run a script to monitor realm authority, and remove build rights from a specific color if the authority is ever to drop (indicating the destruction of a cairn). However, this still leaves a large vulnerability to sabotage in the event of a server crash where the script cannot be restarted right away. It is also annoying because there is no way to tell who the saboteur actually is, since anyone with permissions can bash cairns anonymously leaving no trace behind, so as soon as a cairn is destroyed all the helpers would need to be blacklisted.
It has been suggested before to add a new type of permission to allow for building but not destroying of cairns, but this does not seem to be popular so I will try to think of some other solutions. A timer could be added for destroying friendly cairns, similar to the system for challenging hostile cairns. It would ping the kingdom saying something like 'a cairn was scheduled for demolition' and point to the cairn being destroyed, so people would at least have a chance to investigate and see what was going on. Perhaps kingdoms could have some sort of system log, which would record whenever a member built or destroyed an authority object. Something like '[8:29] MrBunzy destroyed a border cairn'. This would at the very least prevent people from anonymously sabotaging a realm. Maybe make realm cairns a structure that anyone can build, regardless of kingdom allegiance? I can't think of a reason that a kingdom would be opposed to having its borders extended by strangers, and they would be safe from any treachery if the builders did not have any permissions to destroy in the first place.
I think it is bad that such a large portion of the playerbase misses out on the excitement of realm expansion and kingdom territory wars just because of this one mechanic. Recruiting neighbors and acquaintances for realm expansion would also add another social dimension to the game, which would be nice considering how few incentives we have at the moment for player interaction.
Anyone with better ideas to fix pls post. Any devs who read c&i pls consider!