Spectre Robe

The robe and the pants are the fixed half of this armor, and the head you put on top decides what kind of mage you are. Both helmets sit on the same body, so once you have made the pair, swapping costs nothing but an inventory slot. Owning both and switching between them during a fight is how the set is meant to be used, and it is the reason to spend the extra material on the second head rather than committing to one.

Wearing the Spectre Mask, every magic hit throws off homing orbs that go after whatever else is nearby. Their output is governed by a hidden pool that drains as you deal magic damage and refills at a steady rate, which gives the orbs an average ceiling that no damage bonus can lift. What does lift it is critical strike chance, because the orbs roll crits of their own. That inverts the usual accessory advice: a crit-heavy build gains more here than a damage-heavy one, and weapons with unusually high crit rates like the Stellar Tune or Staff of Earth feed the bonus harder.

It also means a defensive build gives up much less than it looks like. If a fixed portion of your output comes from a capped source, reforging every accessory for defense instead of damage costs you nothing on that portion. The orbs cannot set each other off, and a hit too weak to register produces no orb at all.

The Spectre Hood trades away a large slice of your magic damage for healing on every magic hit. The amount returned scales with the damage of the projectile that landed and shrinks for each extra target that same projectile has already passed through, so one heavy hit gives back far more than a wide piercing spray clipping half a dozen enemies. Like the mask it draws on a recharging pool, so you get a strong opening burst and then a steady trickle for as long as you keep attacking.

In multiplayer the orbs do not necessarily come back to you. They fly to whoever on the team is currently lowest, which makes the hood a support piece as much as a survival one.

The damage penalty is applied through the set bonus while the rest of the armor is handing you a damage increase, so the net loss is smaller than the number on the tooltip implies. It is still enough to feel. Stack it with Mana Sickness after a potion and plenty of weapons stop hitting hard enough to sustain the heal, which is the usual reason people try the hood once and put it away. Plan a mana source that is not potions: Magic Cuffs or Celestial Cuffs convert incoming damage into mana, which suits armor that expects you to be standing in the fire, and a high hit rate weapon like the Razorpine keeps both bars comfortable.

Moon Bite shuts lifesteal off entirely, so the hood contributes nothing at all while the tongue is attached, and backing far enough away to avoid it only invites the Moon Lord to teleport onto you. If you insist on the hood there, the play is one enormous hit in the window after the debuff drops and before it is reapplied, something like a Nebula Blaze bolt, since the formula pays much better for a single large number than for many small ones.

It arrives right after Plantera, which is also when Ectoplasm starts dropping, and it takes over from whatever mixed armor a mage was wearing through the mechanical bosses. It holds the slot until the lunar sets. Two smaller things: neither bonus fires on critters, so testing it on a bunny tells you nothing, and the full set makes you semi-transparent, which washes most dyes out as a side effect.