Make sure to kill everything in the area before trying to tame it. If it eats an egg and attacks a stego or something that fights back it'll lose efficiency, just like any other tame. Once you start the process don't let it take any damage.
If you are looking to get a basilisk on crystal isles don’t even try without forcetame or spawn rock drakes due to the drakes not spawning. Thanks for adding acid spitting snakes on the map TAHT CANT BE TAMED