Smaug Mod 1.7.10 adds in Smaug The Dragon as a boss, as well as custom armor, staff and bow (DragonForge). You can also have your own pet Smaug that you can fly anywhere.
How to install:
How To Download & Install Mods with Minecraft Forge
How To Download & Install Fabric Mods
Smaug Mod 1.7.10 Download Links:
For Minecraft 1.7.10