The mechanical bosses were difficult before, but Master Mode brings them to a new level of difficulty. While there are many ways to beat them, there isn’t any better way than this strategy.
It’s not hard to do and only really requires a few items to do, and then you’ll barely have any difficulty beating this once tough boss.
For my last 2 mechanical boss guides I used the Black Spot mount dropped by the Flying Dutchman, and you’re going to need it again for Skeletron Prime. I actually found Skeletron Prime a bit easier than the Destroyer, but he can still be deadly if you don’t use the right strategy.
For armor I used Hallowed Armor with the Ranged Helmet. This armor is perfect because it makes you invincible to attacks for a short period of time, causing you to sometimes not get damaged when you get hit. If you don’t have Hallowed Armor yet then Titanium or Adamantite will work fine.
My accessories were the Molten Quiver and a Ranger Emblem, and the weapon was again the Unreal Daedalus Stormbow. I actually tried using a Hallowed repeater, which seemed to be working but it was much slower than the Stormbow. A Minishark or an Uzi are some other good ranged options to use.
I used an Archery Potion, Ironskin Potion, Swiftness Potion, Regeneration Potion, and a food item for health regen.
Skeletron Prime Strategy
To start off the fight, summon him with the Mechanical Skull and start picking up speed with your mount. Although the mount is fast, he can sometimes catch up to you, which is why the Hallowed Armor is good.
Try your best to never stop moving, because he can stun lock you and kill you in a couple hits. The Holy Arrows I was using seemed to shred his health, and was the fastest option I tried so far.
Normally the best strategy would be to kill his arms first, but while using this mount it’s better to just avoid them and aim straight for his head. This makes the fight a little bit harder, but in turn, lets you kill him quicker for better farming.