CLARIFICATION:
There has been some confusion about NPCs, namely the saboteurs and ability of NPCs to break blocks. I need to stress, NPCs can ONLY interact with blocks that are sabotaged/weakened, and saboteurs cannot sabotage blocks. This suggestion is not to allow for AFK mining or griefing that bypasses banner protection, it is just to allow for a fun self-contained game mode.
Right now, if you want to siege someone's build, and they agree to it, they either have to add you to the banner, remove the banner in it's entirety (both of which may be multiple banners), or open the gate for you. Those are all either a hassle, or just plain looks stupid and is strategically... well, also stupid. My suggestion is that for those who wish to keep main parts of builds safe, but still have it easily siegable for minigames and the like.
Weakened Blocks
So... not sure how well this would be able to be done (code-wise), but there would now be "weakened blocks" This might be a data flag on all blocks, or maybe a special set of blocks that mimic textures of normal blocks. Once again, I'm not sure how this would work. Anyway, these Weakened/Sabotaged/Shoddy blocks would be able to be broken within banner protection by other players as well as hired NPCs, fire, or explosives.
Saboteur's Chisel
This tool is used to "damage" blocks into the weakened state that allows for breaking during siege. This is blocked by banners. The one hosting the event gets to choose what can be broken, not the other way around.
NPC Changes
Saboteurs
Orcish factions as well as tribal factions and a few others (maybe dwarves/some men) would gain new "saboteur" units for use in sieges. They would have something along the lines of 3x sulfur match, 1x fac pick, 1x fac axe, 1x fac/iron dagger (all 3 tools/weapon replaced by mattock for dwarf). They wear light armor for their faction.
Tools
NPCs wielding tools can now use them to break blocks. Those without can also do so, but at a slower speed. NPCs mine at 1/4 speed, but their efforts can stack. In siege mode they will attempt to break fortifications, and will tunnel if there is weakened dirt below a wall. If a flag is in sight they will attempt to move towards it.
- Battleaxes are the most effective against gates
- Hammers gain a mine speed boost against partial blocks such as spike walls, doors, trapdoors, and windows.
- Olog-hammers mine very quickly
Horn of Command - Siege
You can now set a horn of command to siege mode. It is a variant of ready in which NPCs will be able to break weakened blocks, will seek out siege ladders, will light weakened blocks on fire if able, and will very rarely place their own siege ladder if a flag is blocked by a wall. They will also seek out flags as has been noted before.
New Siege Blocks
Palisade Wall
Top blocks in a wall appear to have spikes on top, corners have a single beam. Can be burnt.
A few factions (such as rhudar, rangers, etc) will have forts with palisade walls for single-player siege.
Fortified Wall
Top blocks in a wall appear to have battlements on top.
Siege Ladder
The only block placeable in a bannered region, and then only if there are weakened blocks nearby. It is placed 1-2 blocks back from a wall then pushed into it. after that players and hired humanoid NPCs can climb it to infiltrate a base.
These are also able to be broken by any NPCs/Players. If there are NPCs in a region bannered by their owner they will actively try to break siege ladders.
This will make a 2 block tall ladder, by crafting this with another ladder above it you will gain another block, siege ladders can also be combined in this manner. Height is noted in the block lore.
Spike Wall
A simple fortification which can face in any direction but down. It deals damage-over-time to those touching it, and generates "fall" damage based on speed for those foolish enough to run into its spiky side. Increases normal fall damage if facing up.
Steel Spikes
A reinforced variant of the spike wall. Hammers are the only effective tool against these.Poisoned Spikes
Spike wall/steel spike variant which gives poison when dealing "fall" damage.
Flag (Specialized Banner)
Created by placing a banner on a gemstone block. A flag is the goal of a siege game, and NPCs will try to attack it while in siege mode. The flag would have a textfield to name it with, and when an enemy NPC/Player breaks it, a message like this will appear in chat: "<playername> succeeded in their siege of <flag name>!"
In order for the offensive to lose a siege there would be rules regarding it on the server. It may vary between all players dead, all units dead, or a life system. I would prefer to keep that variability open to servers without a lot of coding that mevans has to do.