There’s a mod available on ASA,the ‘No Untameables’ mod. Firstly,you’ll want to make yourself a deathworm trap (also available in the No Untameables mod) and lure one to you. They really hate the sound of wardrums (mammoth drums included) so that’s a good start. However… once one is caught in the trap… run. A lot more death worms will appear so make sure you kill them and lastly,make sure you have deathworm horns on you,put them into the trapped deathworm’s inventory and boom! You have a deathworm now!