The Necromancer is a hostile spellcaster in Iron’s Spells ‘n Spellbooks that spawns in the dark all over the Overworld, and it only has 25 health. Rather than fighting you itself, it hangs back and raises a small army of armored Zombies and Skeletons, then pins you in place with Root while they close in.
You’ll want to hunt it down anyway, because it’s the only source of the 
Tarnished Crown, a helmet that gives you a big boost to Max Mana and Mana Regeneration. It can be found long before you’ve come across a wizard tower as well, which makes the Crown one of the first pieces of mage gear you’re able to get.
Spawning
Necromancers spawn naturally in every Overworld biome, following the same rules as Zombies and Skeletons, so you’ll find them on the surface at night and in dark caves at any time. They never spawn on Peaceful. One also spawns in a balcony room inside the Catacombs, alongside that structure’s Zombies and Skeletons.
They always spawn on their own rather than in groups, and they’re a fair bit rarer than the common night mobs, so you won’t see one every night. The summon command puts one in front of you if you want to test a fight in Creative first, or just want a quick look at what it does before meeting one for real.
Because they spawn like any other hostile mob, a normal dark-room mob farm can pick up Necromancers too, although at a much lower rate than Zombies. It also means lighting up your base properly keeps them away, which is worth doing early on, since a Necromancer’s summons can wreck an unlit area quickly.
Behavior
The Necromancer fights like a mage that doesn’t want to be hit. It keeps you at range, strafing and backing away, and it’ll run off if you get within about five blocks. Its own melee only does 3 damage, so cornering it takes away most of the threat. As well as players, it goes after Iron Golems and baby Turtles, just like Zombies do.
Attacks
At range the Necromancer mixes three attack spells: Magic Missile, Icicle and Fang Strike, which sends a line of fangs along the ground. Its spells are weaker than most wizards’ though, as it only has 75% spell power, so none of them hit very hard on their own. The damage comes from how often it casts them while you’re busy with its minions.
The part to worry about is its control magic. Root grabs you and stops you walking away, and Blight cuts the healing you get and the damage you deal for as long as it lasts. It also puts up a Fang Ward ring to keep you back, and it drinks potions to heal itself about 6 health each time, which is a big chunk of its 25.
If Root lands while its Zombies and Skeletons are up, you can’t walk away and you’ll be hit from every side. Clear the summons or get out of their reach first, and keep an escape route open before you go after the Necromancer itself.
Raising the Dead
Once per fight, the Necromancer casts Raise Dead, and that’s the reason it’s so dangerous. It summons six or seven undead in a ring around itself, and about seven in ten of them are Zombies while the rest are Skeletons with bows. They stick around for ten minutes, so killing the Necromancer doesn’t make them go away straight away.
Each summon spawns in a random mix of Leather, Chain and Iron armor, so some of them can take a surprising amount of punishment. Along with a Root to hold you in place, this wave of armored undead is where most of the danger in the fight comes from, rather than the Necromancer’s own spells.
Deal with the summons on your terms if it does get Raise Dead off. A doorway or a narrow tunnel stops the Zombies surrounding you, and it takes the sting out of Root, since only one of them can reach you at a time. Open ground at night is the worst place for this fight, as other mobs will join in too.
Defense and Sustain
When you push towards it, the Necromancer backs away and throws up a Fang Ward, and it’ll use Root and Blight more as the fight goes on. It doesn’t have much health though, so a couple of good arrows or a few sword hits finish it off. The hard part is getting to it through its summons, rather than surviving the Necromancer itself.
Fighting from range is the safer way to do it, as a 
Bow or a ranged spell lets you pick it off before Raise Dead goes off, or while its summons are still walking over to you. It only takes a couple of arrows, and killing it early saves you fighting the whole undead wave.
Drops
The Necromancer’s best drop is the Tarnished Crown it wears, which has a 15% chance to drop if you killed it. Each level of Looting adds another 1% to that. It also drops up to four 
Arcane Essence, and when you get the kill there’s a 25% chance of a random low-level Scroll from any school, with Looting improving that a bit too.
Necromancer Drops
The Tarnished Crown gives you 150 Max Mana and 25% Mana Regeneration, and it has its own spell slot, which can be imbued at the Arcane Anvil. The catch is that it lowers your melee damage by 15%, and it has no armor at all, so it’s a caster’s helmet rather than an all-rounder. You can repair it with 
Iron Ingots at an Anvil.
FAQ
Necromancers spawn naturally in dark places anywhere in the Overworld, at night on the surface and in caves, just like Zombies. One also spawns inside the Catacombs. They don’t spawn in Peaceful.
The Necromancer wears it and has a 15% chance to drop it when you kill it, plus 1% for each level of Looting. It won’t drop if something else kills the Necromancer. There’s no crafting recipe for it.
Put it in an Anvil with Iron Ingots, which is the repair material for the Tarnished Crown. You can also combine two damaged Crowns in an Anvil, or put Mending on it if you’d rather not keep repairing it.
No, the Necromancer isn’t classed as undead, so Smite does nothing extra against it. The Zombies and Skeletons it summons with Raise Dead are the undead part of the fight, and Smite works on them.
