Crossover content

Crossover content is content added from a different game, while the other game also adopts some content from Terraria, with mutual permission. Homages and references, however, are not crossover content.

Edge of Space
Edge of Space is a 2D sandbox game developed by Handyman Studios, similar in gameplay to Terraria, but in a space setting.

Reciprocal content
Edge of Space has a boss, "Omegatron", which is based on Skeletron.

Pixel Piracy
Pixel Piracy is a 2D real-time strategy game developed by Quadro Delta and published by Re-Logic. To celebrate the publishing deal, version 1.2.4 added crossover content into Terraria.

Reciprocal content
The weapon Starfury is present in Pixel Piracy.

Dungeon Defenders 2
Dungeon Defenders 2 is a 3D tower-defense game developed by Trendy Entertainment which has crossover content in Terraria since version 1.3.4. Its setting is called "Etheria" so elements from this game are called "Etherian" to distinguish from the Terrarian versions when ambiguity could exist, such as for example between Etherian Mana and Mana, or Etherian Goblin and Goblin.

The game features four core classes, which are represented in Terraria by the selection of player equipment. Sentries and armor sets are bought with Defender Medals from the Tavernkeep when the corresponding tiers are unlocked (Tier 1 is available from the start, one Mechanical Boss defeated in Hardmode for Tier 2, Golem defeated for Tier 3). Tier 2 weapons and accessories are dropped by the Ogre while Tier 3 weapons are dropped by Betsy. Other content include:
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 * Old One's Army
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 * Old One's Army
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 * Old One's Army

All the crossover content in Terraria is obtained through the Tavernkeep NPC, either directly from him or indirectly by triggering the Old One's Army event.

Reciprocal content
As part of the crossover, Dungeon Defenders 2 incorporated some Terrarian content as well.
 * The Dryad became an additional hero class, able to use Vile Powder, Purification Powder, Fallen Stars, Slimes, Harpies, Moss Hornets, and Angry Nimbuses to attack enemies. She also retains her Dryad's Blessing, and can use Leaf Wings. In that game, she is also able to transform between her normal form and a corrupt form, modifying the effects of her powers.
 * Many Terraria weapons became available for certain heroes, such as the Meowmere, Lunar Portal Staff, Demon Scythe, Tsunami, and more.
 * A new map, the Forest Biome was added, featuring Demon Eye enemies, the Eye of Cthulhu boss, and various other Terraria elements.

Minecraft
is a 3D sandbox game developed by which has crossover content in Terraria since 1.2.1.
 * One of the title messages says: "Terraria: Also try Minecraft!"
 * One of the title messages says: "Terraria: Also try Minecraft!"

Reciprocal content

 * has officially claimed that the summon mechanism of The Wither, one of Minecraft's bosses, was inspired by the boss summon mechanics of Terraria.
 * One of Minecraft's title screen splash messages says: "Also try Terraria!".

One Drop
One Drop is a yoyo manufacturer. In 1.3.0.1, these following One Drop's yoyos were added to Terraria:
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Reciprocal content
In turn, One Drop released real-life yoyos designed after and.