I’d highly recommend using a good imprinted managarmr to tame this. They don’t damage element veins with their ice breath and are small enough to NOT aggro the dread. Simply feed the big guy some element and kite him to an alpha element vein (smaller veins give significantly less taking effectiveness). Then, fend off waves of corrupted creatures (you cannot hurt the dread by attacking, don’t worry). They get a significant attack and defense buff against large creatures like gigas and extinction titans. I’m breeding 5 to take them on right now!