What the game says, what really changes when you play, and the code to unlock it. Steam says 12.4% of players have it.

Artifact of Evolution
Game text: «Monsters gain items between stages.»
At the end of every stage, all monsters gain an item (white at first, later greens and reds). The items show above their health bar.
For a harder long run. Enemies with Ukulele, AtG Missile or Tougher Times change fights a lot; from the loop on it gets really hard.
It is in the base game. 12.4% of all Risk of Rain 2 players on Steam have it, from Steam's public stats on 31 October 2026.
Read top to bottom, as shown here: three rows of three shapes. Each slot on the generator changes shape when pressed, in this order: square ■, circle ●, triangle ▲, diamond ♦.
In co-op, the group can enable any artifact that any player has unlocked. Artifacts are chosen in the menu before the run starts.
Enter its code (♦♦♦ / ■■■ / ●●●) in the Compound Generator on Sky Meadow or Helminth Hatchery, use the laptop and beat the Bulwark's Ambry trial: take the key and break the reliquary.
At the end of every stage, all monsters gain an item (white at first, later greens and reds). The items show above their health bar. For a harder long run. Enemies with Ukulele, AtG Missile or Tougher Times change fights a lot; from the loop on it gets really hard.
12.4% of all Risk of Rain 2 players on Steam have it, from Steam's public stats on 31 October 2026.
Sources: the game's English text (artifact name and description), the Risk of Rain 2 wiki (riskofrain2.wiki.gg: the Artifacts page and this artifact's page, read on 31 October 2026; code, Compound Generator and Bulwark's Ambry) and public Steam stats. The plain-words text is ours. Icons: Risk of Rain 2 (Hopoo Games / Gearbox).