'Variants' are alternative versions of Spore Mobs, typically having a unique texture and model. Variants can give Mobs different stats, cause them to inflict certain effects, or grant them unique abilities. Evolved and Organoids are the main tiers that get Variants, though some Infected and Utility Abnormal have them as well. For Evolved, the maximum amount of different Variants they can have is four. This limit does not exist for Organoids. Additionally, Evolved that have Variants do not have a Hyper Evolved form, nor will they ever receive one.
Traditional spawning of Variants is by a percent based roll when a Mob first spawns. Each Variant a Mob (including its 'base Variant') has presents an equal chance to spawn (e.g. Protectors have an 80% chance to spawn as one of their four Variants (excluding normal Protectors), with an overall 20% chance per Variant). The only exception to this is Raid Captain Infected Pillager Variants and Bunker Buster Tumoroid Nuke Variants, which both have a unique 20% chance to spawn.
Some alternate versions (which are technically considered Variants in the code) have unique spawning conditions and thus are not considered proper Variants, nor are they listed here. This includes Infected Villager Biome Variants, Infected Diseased Villager Biome Variants, Drowned Scampers, Villageroid Scampers, Hallucinations, and Verfalldrache Head Variants. Despite Infected Adventurer Skin Variants technically not having unique spawning conditions, they are also not listed here due to the large number of them, as well as the fact that they have no unique abilities.
Mob Variants can be instantly swapped and cycled by right clicking them with a Mutating Syringe.
It's important to note that 'skins', 'Attributes', 'Adaptations', and 'outfits' are not the same thing as Variants.
Skins are gained from Mobs having a specific name applied to them. This includes Infected Adventurer Name Variants, Braiomilfs, Spooky Gorgons, Omni-Man Groberfubs, and Nunny Proto Hiveminds.
Attributes are a mechanic exclusive to Calamities and the Womb Crafting System.
Adaptations are a mechanic exclusive to Calamities that occur under specific circumstances.
Outfits are seasonal attire given to certain mobs during a certain period of time. This includes 'Festive Proto Hiveminds', 'Santa Siegers', 'Christmas Tree Howitzers', and 'Star Light Hindenburgs'.
The icon for Variants.
Trivia
Despite Bairn Variants seeming to exclusively spawn from unique conditions, they can actually spawn from percent based rolls if spawned by a Swarmer Howler Variant or spawn egg.
Interestingly, right Howitzer Arms are not considered as Variants in the code (despite the different Verfalldrache Heads technically being considered as Variants).