Terraria Secret Seeds

Both evil biomes are present, ores that have two variants spawn both, and the dungeon is now under a living tree. Replaces the Guide with the Party Girl

The Jungle biome dominates most of the world using this seed and The Guide is replaced with the Merchant

Difficulty upscaling, (If you choose Classic mode it will instead choose Expert.) and introduces a new difficulty mode called Legendary, adding some AI changes. Boss AI changes include; Eater of Worlds splits into Eaters of Souls, the Brain of Cthulhu flips your camera upside down in the second phase, Skeletron's head reflects projectiles when spinning and he will summon Dark Casters if you destroy his hands. Bunnies are always replaced with Explosive Bunnies, and Demons are replaced with Voodoo Demons. Lit bombs sometimes drop from shaking trees, some water pools are replaced with lava pools, Skyware Chests are replaced with locked Gold Chests, and some bosses receive changes to size and/or AI. Guide is replaced with the Demolitionist

Celebrating Terraria's 10th birthday, the player spawns on the beach of one of the world's Oceans. The Guide, Steampunker, Princess, Party Girl, and Town Bunny also spawn and a Party immediately starts. Most of the world is painted in bright colors, and items in chests always have a "best" modifier. The Jungle Mimic and Golden Slimes can also spawn.

This seed introduces hunger and darkness mechanics, making the early game very challenging. Marble biomes and Spider Caves can generate on the surface, touching Cacti will damage the player, and also adds a dark filter to the world. Added with the Don't Starve crossover.

Despite its name, this seed substantially increases the amount of traps generated, such as Dart Traps, Explosives, and Boulders. It also introduces a new and more dangerous version of the Boulder, the pink Bouncy Boulder.

Commonly called the Remix seed, it flips the usual order of progression by spawning the player in the Underworld, and things that would normally happen in the Surface layer instead happen in the Underworld. The center of the Underworld consists of an island of Ash with Ash Trees and Ash Grass, with no lava or Hellstone. With the exception of Lava Slimes, regular Underworld enemies are replaced by surface enemies as long as the player stays on the island. The Surface is entirely covered by either the Crimson or Corruption, depending on the world evil, and it is always night. Mimics also spawn in pre-Hardmode, but only drop their standard loot in Hardmode. Fallen stars can sometimes drop from pots and slimes, and the Jungle Temple spawns on the Surface. Shop NPCs always sell pylons if there is at least one other NPC nearby. The Guide is replaced with the Tax Collector.

This seed is a combination of all the previous seeds. A Party immediately starts, but when it ends, the Tax Collector, Steampunker, Princess, Party Girl, and Town Slime will all instantly die. Along with this, the Steampunker will not sell the Clentaminator or any solutions. All three Mechanical Bosses have been combined into one mega boss, called Mechdusa, spawned by using the Ocram's Razor. When killed, it will drop this seed's exclusive weapon called the Waffle's Iron. More boss AI changes include; Empress of Light will only enrage if spawned on the world's surface, and Moon Lord shoots Boulders which behave similarly to Bouncy Boulders.