Well, Playing ark mobile you can get leech blood in swarmp area. just go there and go all out, just run in the swamp like a mad man with you op tame you kill leech and get the leech blood in tame inventory, dont try to search this leech cause it really hard to spot them.. Just make sure that tame can survive any threat in the swamp in case you got disconnected in the game.. dont know why I also get Angler in the swamp while running like a mad man in there.