The Twins Terraria boss · Hardmode · #10 in the usual order

Two mechanical eyes, Retinazer and Spazmatism, linked by a cord. They are a much harder take on the Eye of Cthulhu and one of the three mechanical bosses. Both must be killed, and they drop Souls of Sight.

Stage: Hardmode
Required?: Needed to progress
Summon: Mechanical Eye
Where: Night, on the surface
Max life: 43,000 (Classic)
Defense: 10

Biome: Space

Stats by difficulty

Stat	Classic	Expert	Master
Max life	43,000	64,500	82,237
Damage	Varies by part and attack

Parts
Part	Classic	Expert	Master
Retinazer First Form	20,000	30,000	38,250
Spazmatism First Form	23,000	34,500	43,987

How to summon The Twins

Mechanical Eye. Use a Mechanical Eye at night. Craft it from 3 Lenses, 5 Iron or Lead Bars and 6 Souls of Light at a Mythril or Orichalcum Anvil. Once an altar has been broken, there is also a 1 in 10 chance each night that one of the unbeaten mechanical bosses appears on its own.

Attacks and phases

Retinazer fires lasers from above at an angle; Spazmatism shoots cursed flames from the side. Both charge like the Eye of Cthulhu.
Each eye changes form at 40% health.
Retinazer's second form becomes a laser cannon that fires fast bursts.
Spazmatism's second form breathes a cursed flamethrower and dashes often.

Strategy

Build a long sky bridge with Campfire, Heart Lantern and a Star in a Bottle.
Focus one eye at a time; many players kill Spazmatism first since its flames are deadly up close.
Keep running in one direction to outpace the lasers.
Wings make dodging the charge attacks much easier.
Bring Ironskin, Regeneration, Swiftness and Endurance potions.
They leave at dawn, so summon them right after nightfall.

Recommended weapons

Melee

Adamantite or Titanium Sword, or the Amarok yoyo

Ranged

Clockwork Assault Rifle, or the Megashark if the Destroyer is down

Magic

Crystal Storm or Golden Shower

Summoner

Spider Staff with the Cool Whip

Armor and gear for each stage.

Drops

Item	Qty	Chance
Soul of Sight	25-40	100%
Hallowed Bar	15–30	100%
Greater Healing Potion	5–15	100%
Twin Mask	1	14.29%

Expert and Master Mode extras

Mechanical Wheel Piece Expert · 100%

Pair of Eyeballs Master · 25%

Twins Relic Master · 100%

Classic Mode rates. In Expert and Master Mode most loot comes in a treasure bag , which also holds the Expert-only Mechanical Wheel Piece.

After you beat The Twins

Souls of Sight and Hallowed Bars for Hallowed armor, the Optic Staff and the Pickaxe Axe/Drax
The Steampunker can move in after your first mechanical boss
With all three mechanical bosses beaten, Plantera's Bulb grows in the Jungle

Did you know? When they spawn on their own, the game warns: This is going to be a terrible night...

FAQ

How do you summon The Twins in Terraria?

Use a Mechanical Eye at night. Craft it from 3 Lenses, 5 Iron or Lead Bars and 6 Souls of Light at a Mythril or Orichalcum Anvil. Once an altar has been broken, there is also a 1 in 10 chance each night that one of the unbeaten mechanical bosses appears on its own.

How much health does The Twins have?

43,000 in Classic, 64,500 in Expert and 82,237 in Master Mode.

What does The Twins drop?

Soul of Sight, Hallowed Bar, Greater Healing Potion, Twin Mask, plus the Mechanical Wheel Piece from the Expert Mode treasure bag.

What should I use against The Twins?

Melee: Adamantite or Titanium Sword, or the Amarok yoyo. Ranged: Clockwork Assault Rifle, or the Megashark if the Destroyer is down. Magic: Crystal Storm or Golden Shower. Summoner: Spider Staff with the Cool Whip.

Sources & picture credits

Guide text is original retrogameindex writing, checked against the Terraria Wiki. Boss statistics and drop rates are the game values shown in the Terraria Wiki’s infoboxes. Sprites and artwork © Re-Logic; local copies archived from Terraria Wiki file pages (listed on the image gallery).