New extinct mobs and bosses

My idea: new extinct mobs and bosses. Something like a sniffer but hostile that can push the player back and damage it as a boss. Maybe 2 peaceful mobs too, like a mushroom themed extinct mob. It would fight hostile mobs and defend the player (the mob would be tameable). To find it the player would need to go to a new structure and find its egg. The structure would spawn only in Mushroom Islands and would have a new block called "Old Mycelium", which could be inspected by the player to get three items: two new pottery sherds and the egg. The second mob would be something like a snow mob, maybe a small mob that can be tamed. To find it, the player would need to find a igloo with basement. The player would need to break the floor to find a secret chest with the egg. Also, try to add fried egg.