Evolution is a fundamental mechanic introduced by Fungal Infection: Spore that allows Spore Mobs and Blocks to be able to Evolve into stronger forms, overall acting as an essential key to the infection's progression.
'Evolution' is an umbrella term, as there are four main (informal) categories of Evolution; 'basic Evolution', 'Hyper Evolution', 'failed Evolution', and 'Linked Evolution'.
All forms of Evolution have a few requirements for it to go underway; this commonly includes Evolution Points, but also what is known as an 'Evolution timer', which is just a set amount of time that must take place before Evolution can occur. Evolution timers start when all other requirements are met. If a Mob has an active Evolution timer as well as Frostbite, the Evolution timer will be paused until the Mob no longer has Frostbite.
When a Mob Evolves, a burst of smoke particles will briefly appear before the Mob transforms. Additionally, when Evolving, Mobs will keep any Kill Points, Evolution Points, a Search Position, if they're Linked, and if they have a custom name.
Instant Evolution can be caused by Proto World Modifier (30% chance for an Evolvable Mob to Evolve as soon as it spawns) and Mutagenic Reactant (10% chance when an Evolvable Mob is hit with a Weapon that has Mutagenic Reactant to Evolve). Instant Evolution ignores all requirements and skips Evolution timers.
Evolution Syringes and the /spore:evolve command allow players to manually Evolve Mobs.
Evolution tree/progression map.
An Infected Villager Evolving into a Bomber Spitter Variant (left) and a Knight Hyper Evolving into an Inquisitor (right).
If an Infected tier Mob obtains at least 1 Evolution Point, a 5 minute Evolution timer will begin. Once the Evolution timer expires and the Infected is still alive, it'll Evolve into one of its available Evolved forms. Every Infected has between three to four possible Evolved forms they can become (excluding Infected Drowned). The possible transformations go as follows:
Infected Human → Knight, Griefer, Braiomil, and Phayres (any given Evolution has a 22.5% chance to spawn)
Infected Husk → Verdathorn, Jagdhund, and Scavenger (any given Evolution has a 30% chance to spawn)
Infected Drowned → Bloater and Naiad (any given Evolution has a 45% chance to spawn)
Infected Villager/Infected Diseased Villager/Infected Wandering Trader → Leaper, Slasher, and Spitter (any given Evolution has a 30% chance to spawn)
Infected Witch → Volatile, Mephitic, and Gorgon (any given Evolution has a 30% chance to spawn)
Infected Pillager → Howler, Stalker, and Brute (any given Evolution has a 30% chance to spawn)
Infected Adventurer → Nuckelavee, Protector, Charger, and Gargoyle (any given Evolution has a 22.5% chance to spawn)
Normal Infected Scientist Variant → Conductor (100% chance to spawn)
Tank Infected Scientist Variant → Chemist (100% chance to spawn)
Coat Infected Scientist Variant → Inebriater (100% chance to spawn)
If an Evolved tier Mob (that has a possible Hyper Evolved form, meaning it has no Variants) obtains at least 7 Evolution Points, a 10 minute Evolution timer will begin. Once the Evolution timer expires and the Evolved is still alive, it'll Hyper Evolve into one of its available Hyper Evolved forms. Evolved that have a Hyper Evolved form only have one possible form they can become. The possible transformations go as follows:
When an Infected (excluding Infected Scientists) attempts to Evolve into an Evolved form, there is a 10% chance that Evolution will fail, and the Infected will become a Scamper instead. Depending on the Infected that failed Evolution will depend on the resulting Scamper Variant. The possible transformations go as follows:
Infected Human/Infected Husk/Infected Adventurer → Normal Scamper Variant
Infected Villager/Infected Diseased Villager/Infected Wandering Trader/Infected Witch/Infected Pillager → Villageroid Scamper Variant
Additionally, from this branch of Evolution, Gastgebers can be formed. If a Scamper obtains at least 7 Evolution Point by the time its 10 minute age timer expires and the Scamper is still alive, it'll Evolve into a Gastgeber. Gastgebers also have a 30% chance to Evolve from Linked Scampers when their 10 minute age timer expires, regardless of how many Evolution Points they have.
Once a Scamper has existed for the duration of its 10 minute age timer, if it doesn't Evolve into a Gastgeber, it'll transform into 2 to 3 Mounds. When a Mound is at the maximum Age it can be, it'll become capable of placing a Reconstructed Mind Block. These Blocks will call nearby Spore Mobs to walk towards them and give them their Kill Points. When Reconstructed Mind accumulates 40 Kill Points, it'll transform into a Proto Hivemind. When this happens, the message "Endure..." will be sent in chat. However, if there's already a Proto Hivemind within 300 blocks of the Block, it'll become an Outpost Watcher instead.
Additionally, upon a Proto Hivemind's death, her Brain Remnants are capable of turning into a Hivetumor. When this happens, the message "Regrowth..." will be sent in chat. Once a Hivetumor has existed for 1200 seconds (20 minutes), she'll Evolve back into a Proto Hivemind. When this happens, the message "Endure..." will not be sent in chat. However, if there's already a Proto Hivemind within 300 blocks of the Hivetumor, she'll instead despawn and give 1000 biomass points to the nearest Proto Hivemind.
Some Mobs have unique forms of Evolution that can only occur when they are Linked.
Infected Diseased Villager → Reaper
When a Linked Infected Diseased Villager has at least 1 Evolution Point, after waiting for its 5 minute Evolution timer to expire, it'll become a Reaper.
Infected Wandering Trader → Specter
When a Linked Infected Wandering Trader has at least 1 Evolution Point, after waiting for its 5 minute Evolution timer to expire, it'll become a Specter.
Raid Captain Infected Pillager Variant → Vanguard
When a Linked Infected Pillager Raid Captain Variant has at least 1 Evolution Point, after waiting for its 5 minute Evolution timer to expire, it'll become a Vanguard.
When a Linked Scamper's 10 minute age timer expires, it has a 30% chance to become a Gastgeber, regardless of how many Evolution Points it has.