The Necromancer is a large skeleton that wears blue turfs, a cape with blue stripes near the end, a golden belt with a blue gem in the middle, has greenish eyes, and wears a gold crown-like headwear. Necromancers always hold a staff with a blue orb placed upon a stick. The Necromancer is one of the most powerful non-boss hostile mob in Minecraft Dungeons, along with Royal Guards, Wraiths, Spawners, Leapleaves, Enchanters, Geomancers, Diamond Armored Pillagers, Ravagers, and Diamond Armored Vindicators. They are also the only non-boss mobs that have a staff with an orb. the Necromancer is known as the Summoner. gamepedia page

https://minecraft.gamepedia.com/Minecraft_Dungeons:Necromancer