Deep Dark Mobs

I think the warden is a good idea, but if it is the only mob that makes the deep dark hard to traverse it wont have the same "first night feeling". It is like the creeper. The warden with smaller hostilities would be better, such as newer iterations of past mobs.

I think the addition of a new spider would be good, the cave spider was interesting. Having the ability to poison you. It then a newer one would, it's environment, Have you wanting to avoid it. It should: give you slowness, making you easier prey/ inflict you with a strong blindness, so that even torches barely help. The spiders, because of stronger prey, have stronger cobwebs which immobilize you unless cut with at least a iron level pick.

I would say that it is enough zombies already, but hear me out. A zombie that you'll have to listen for. it unlike the other mobs, evolved without luminesce and are quick on their feet. When hit they make a loud noise, warning any mobs in a 5-10 block radius. If they hit you, would be inflicted with mining fatigue for a decent amount of time.

All of these mobs will be like the warden, detecting you by sound.

If you see this, I thank you for taking time to read this, and I hope you take this into consideration.