Evolution: Mecha vs Mutant explained

Evolution is a primary stat added by Primal Dread. A positive value pushes the run toward Mecha: enemies become laser-firing mecha dinosaurs and drop Mecha Parts, which you spend in the shop to mechanize weapons. A negative value pushes it toward Mutant: enemies become acid-spitting mutants and drop flasks that mutate your items, either removing a penalty or copying an effect onto a new item, the Tumor. You choose the side by which drops you pick up.

How Evolution moves

Source	Evolution	Notes
Mecha fruit	+1	Consumable dropped by enemies
Mutant fruit	−1	Consumable dropped by enemies
Jamming Backpack	+5	Hits slow mecha enemies by 50% for 2 seconds
Shaving foam can	+1 or −1	Two versions; each raises that side’s spawn chance
Evolved Leap	+2 or −2	Multiplies your Evolution by 2 when equipped
Boosted Mitosis	−3	+50% chance for mutated enemies to drop a mutation fruit
Eldritch Figurine	−5	50% chance to heal 1 HP on a mutated-enemy kill
Droid	+1 per wave	Can only evolve on the Mecha side
Mad Scientist	+2 per wave	Every change feeds both sides

To stay on one side, leave the other colour’s fruit on the ground. Players report that after about three points on one side the opposite fruit stops appearing and the side’s resource starts to drop: circuit-board Mecha Parts on the Mecha side, green flasks on the Mutant side. The developers have not published that threshold.

Mecha: mechanizing weapons

Mecha Parts drop from enemies with a 1.5% chance since 12 November (2% at launch). In the shop, the Mechanize button on a weapon spends parts and asks you to pick one stat option.

• Each mechanization adds mecha power, worth +3% weapon damage per point. A weapon mechanized 8 times deals 208% of its base damage (280% before the patch).
• Stat options grow from tier I to tier IV values over ranks 1 to 8 and stop growing after rank 8. The part cost keeps rising.
• Hovering the button previews the new stats in green. After you press it, the stat choice cannot be cancelled.
• The mechanized weapon keeps its slot. It no longer gains piercing or bounces.
• Mechanized weapons also appear in the shop. Dismantling one gives Mecha Parts for a material price; Titanium Excess cuts that price by 25%.
• A player in the Steam discussions reports that cursed weapons cannot be mechanized.

Mecha enemies fire lasers and leave oil puddles that slow you. Plastic Boots make you immune to puddles.

Mutant: mutations and the Tumor

Mutant enemies drop a green flask; the patch notes call it a mutagen in 1.2.0.1 and the Mutation Fruit on 12 November. Its base drop chance is now 4%, falling by 1% every 10 waves from wave 30, to a minimum of 1%.

A mutation does one of two things:

1. Removes a malus from an item. The item is then shown as mutant.
2. Copies one effect from an item onto the Tumor, a special item that collects copied effects. The Tumor’s first line counts your mutations, and repeated copies of the same effect merge into one line.

Copied effects get stronger as Evolution moves further toward Mutant: 70% strength at 40 points and full strength at 100. From 40 points, pets, structures and some other effects can also be copied. Effects that would do nothing are skipped, for example a second copy of Anvil, Treasure Map above 100%, material attraction above 100%, Snail at minimum enemy speed and Extra Stomach at its per-wave cap.

Mutation modifiers:

• Variant mutates once at the end of every wave and has a 25% chance to mutate an item when you equip it from the shop or a crate.
• Chimera Cells, new on 12 November, add +10% chance to mutate an item when equipped, up to 5 copies. Winning with Variant unlocks them.
• Wildfire Mutation gives a 25% chance that a mutating item is replaced by a mutated item of a better tier. It is unlocked by default since 12 November.

Mutant enemies leave acid puddles. Since 12 November the acid ticks as soon as you step in and stops when you leave.

Choosing a side

Your run	Side that fits	Why
Few weapons you will keep to the end, such as one tier IV class	Mecha	Each mechanization raises that weapon’s damage and stats
Many items with large single effects (regeneration, armor, pets)	Mutant	Copies duplicate effects, and maluses can be removed
You dislike being slowed or need room to kite	Mutant	Acid hurts only while you stand in it; oil slows you
Droid	Mecha only	The character cannot evolve toward Mutant
Variant	Mutant only	The character cannot evolve toward Mecha
Mad Scientist	Both	Enemies evolve into either camp with equal chance

Before 12 November Mecha was the stronger side; the developers named “Mecha that felt overpowered” and “Mutant that felt underpowered” as the patch’s first goals. Advice written in the first launch week, including damage numbers above 800 on mechanized guns, describes the older +5% rule.

Items that care about evolved enemies

Exothermic Reaction gives evolved enemies a 33% chance to explode on death. Flare gives +1 material per evolved kill but adds 20% enemy damage and 10% more enemies. Virus can charm evolved enemies below 50% health.