This doesn't exist in Minecraft; it's just fictionObsidian Dragons are Dragons found in the Possible World and their Eggs can be found in Abondoned Mineshaft Chests and Strongholes.
They are usually airborne, but sometimes can land. Obsidian Dragons are not cutscene bosses, and behave exactly the same as regular Ender Dragons. If provoken, they will become as hostile as Ender Dragon and tameable with Leether Porkchop when not provoked. However, they fly at extreme altitudes and shoot fireballs that explode and leave behind a huge crater. They have the health between Ender Dragons and Nova Dragons and have the same death animation, however during this period a death they slowly turn white then dies. They are required to be saddled to be rode on and control. When killed, they drop Obsidians, Obsidian Hammer and 100 XP Orbs.
They are found in Possible World where many Obsidians are and rarely about 10% found in Volcano Biomes in the Overworld or other Dimensions (besides The End, The Nether, The Afterworld, The Descent, Far Lands, Brillaria and more), and Eggs which can be found in Abondoned Mineshaft Chests and Strongholes.