The checklist
- Max the weapon. Keep picking its upgrade until the level-up menu stops offering it.
- Have the right passive. See the evolutions list for which passive each weapon needs. Any level works, per player reports.
- Open a chest. Elites and bosses drop weapon chests. With both conditions met, the chest triggers the evolution.
Why it isn’t working
- The weapon is one level short — easy to miss when two weapons share a name family (Boltgun vs Boltstorm Pistol are different weapons in different universes).
- The passive is for a different universe. 40K and Age of Sigmar have separate item pools; the Tape Measure that evolves the Chainsword won’t help an Age of Sigmar axe.
- The weapon had no evolution in the demo. Power Fists only evolve in the full game (and the evolution summons Marneus Calgar).
- The chest spawned somewhere you can’t reach. Known demo bug, fixed for launch according to Auroch.
Squad weapons
If your character’s keywords don’t allow a weapon, a follower appears and uses it for you (the Squad system). Followers’ weapons can still be levelled and evolved — the Apr 9 post describes evolving Power Fists to bring Marneus Calgar into your squad.