To unlock all stuff from swamp you need to kill all mobs there.
- draugr (entrails)
- elite draugr (trophy)
- leech (bloodbag)
- blob (guck - also mineable at some trees)
- ooze (ooze? and sometimes scrap iron)
- wraith (chain)
- abomination (roots)
Additional but not necessary for new stuff: surtlings for cores and coal, their trophy is a nice little light, that doesn't need fuel.

Scrap iron (drops sometimes from ooze or mined in crypts) needs to be smelted, pickup the ingot!

- find a turnip seed plant and cultivate it, pick up the turnip then. The plant sometimes is hard to find, pretty rare. Don't give up watching out for a little yellowish plant like the carrot plants in dark forest.

- chop an old tree to get ancient bark (also in chests in crypts) the big ones are indestructible but the small ones can be chopped.

Good luck and take care, swamp can be dangerous;-)