It does 0.8 damage, and weak potions only heal for 0.7. I can't figure out how to get medium potions. I tried alchemy, but I couldn't find all of the ingredients required.
using wind attacks should do the trick, just take the tentacles in small doses so you don't die, then after killing one or two and getting the tentacle juices, go upgrade your stats at the witch hut in the desert and you should be ok from there.
