I was playing today, going through a swamp collecting dragonflies, getting bit by midges and thought it would be cool to have a swamp terrain credo.
Some examples of what could be possible rewards would be :
Improved quality on plants found in swamp.
Improved quality on creatures found in swamp.
Faster (unmitigated) movement speed in swamps.
Immunity to midges.
Quests could follow the same format as other credos:
Deliver X to quest giver. X being a swamp related item.
Eat Frog legs or Candleberry or lizard on a stick.
Study X curio.
Pick X plant y times.
Capture x creature y times.
There's a few problems overall that would need tweaked. The quests might be too easy when compared to some other credos. Immunity to midges (and the credo in general) promotes swamp botting. It would only be useful to people who happen to be near a swamp. But overall I think it could be an interesting credo to add. Maybe put it with mystic as the pre-req for getting it or something. Whatever works best and makes logical sense.