Wither Skeleton Spellcaster Boss

A wither skeleton with 200 health (he ignores enchantments so sharpness and fire aspect or smite don't work on him) that works like an evoker but when he flail his arms he summon wither skeletons (instead of the vex mob) and soul fire charges that work like blaze fire charges but are slower and the health you lose from the fire that they inflict after hitting you directly is added to the spellcaster (if it falls on the ground the fire does what regular soul fire does, it just burns you) and when at half health it get a reflection shield (like the wither) and can also teleport within 5-8 blocks away from you ( but if it get more than 8 blocks away from you it will on you). It's drop would be the "Soul of the Nether" which when equiped on your left hand (or your right hand) it gives you the "Soul of the Nether" effect which allows you to regenerate health even if you don't have the required hunger, fire resistance and when you die it works like a totem of undying but it also gives resistance 2 for 10 seconds.The way you summon it is by making the wither's base, place a wither skull on the right and left side then in the middle you light the soul sand/soil on fire and then you throw a nether star in that fire.