The Wither Dragon

The Wither Dragon is a modded experimental hostile boss mob introduced in a video called "I Bred a CREEPER and VILLAGER together in Minecraft!". It flies around shooting dragon head projectiles that explode upon contact with a solid object. The projectiles have about the destruction power of a TNT blast, and it causes fire that can spread. It is not fire immune and is vulnerable to arrows, a diamond sword, and the like. It almost trapped Dan in a gravel avalanche.

Quotes from Dan describing the mob:
"Look at it! It's got three dragon heads, it's got the Wither's body, but it's also got the Ender Dragon's wings!" "Whoa! Oh my goodness, I have to get out of here QUICK!"

"So this guy fires, instead of wither skeleton heads, just like the wither does, it fires off ender dragon heads, which as you can see, are pretty powerful."