If dragons are put in 1.9 or so on dragon armor should be put it and it would let you go in lava but would deplete in usage the longer you're in lava til its gone. Dragon weapons as well with fire attributes. Spiders could have poison attributes making them a deadlier foe and they could drop poison sacks that could add poison attributes to your weapon through crafting. Snakes could be a new passive mob and you could make snake skin clothing and would have the same strength as leather armor. I felt I was a bit vague with the dragon stuff if you want me to explain something I'll try. Build on it!
I wasn't aware of that. Then they could have the poison sack drop to that and make spider armor poison resistance and something else.