How do you get the level 16 plane caster on fusion fall

first of all i hope this helps you i am new to fusion fall and i also need help but i do have some friends who are THE FUSION FALL MASTERS and i happen to get a lot of tips and tricks from them and one of them was how you get plane casters (crossbows) that is what i like to call them. STEP1 go to habitat homes take a mission from billy and Mandy (the grim adventures of billy and Mandy) and this is what my friends told me so i am very sorry if i gave you the wrong information PEACE OUT HOPE THIS HELPED