With all the horrible things and disastrous events that can assail your fortress, how about some very rare creatures that might aid fortresses-in-need that the cross on their travels. For starters i was thinking about things like for example Grove Tenders and Mountian/Hill giants. They would start life in good biomes and then travel the world helping good civs in need. As previously stated, these good Samaritans would be quite rare, but more likely to appear when your fort is in great distress.
For example Grove Tenders (Semimega):
A small group of these centaur like creatures may appear in times of famine. Their ability would be use their magical affinity with nature to terraform a small area to be a lush garden with some grown wood, a group of fruitbushes and some cloth-fiber plants. After this is done they make their leave. *requires good relations with elves*
Mountian Giants (mega):
These great, hearty and bearded giants share a lot in common with their dwarven kin: Affinity for metal and stone, love of beer and (as previously stated) lush beards among other things. Unless you make an effort do drive them off with hostility, these wardens of the mountains might stop by and give you some food, useful metal or tools in exchange for a hefty amount of rum and some good laughs before leaving. They might also arrive armed with large clubs in an attempt to save the day from a devastating siege. They give dwarves good thoughts for their presence. *requires to be dwarves only an issue if you mod in other playable races*
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These creatures would prefer to run away if attacked, only striking back if trapped.
Semimegabeast Mercinaries:
Some Cyclopes and Minotaurs might arrive to offer their services for a large amount of food and/or some valuable goods instead of outright attacking you. The fee is seasonal and if you can't pay for another stay they'll make their leave. A good idea if you suspect a siege will knock at your doors soon. These creatures WILL attack if attacked however.
What do you think about this? I think it would add a neat amount of depth to the game.