ActiveAI is a server side mod that greatly increases difficulty. It is experimental, it may or may not be developed and updated.
Currently implemented features:
- Zombies are breaking blocks to reach targets, can even mine stairs up and down
- Creepers are blowing blocks placed by player
- Increases follow range 5 times by default (configurable)
How I would like to make this mod look in the future:
- apocalypse mode - every zombie and creeper breaks player's blocks
- attacks mode - attacks (like raids) spawning every some time near player's buildings to destroy them, attack size based on building size
Dev commands:
/by_player [pos] - test if block is placed by player
I will port it to Forge if this mod become a bit popular.
Suggestions, feedback, bug reports are welcome.