For clarity: “+1” here means +1 extra stat line on each weapon upgrade. It does not guarantee specific numbers for each stat line.
Megabonk’s Items index includes a handful of run-defining pickups—Anvil is one of the most impactful because it improves every future weapon level you take after acquiring it. The extra stat line compounds over time, so the earlier you secure Anvil, the stronger your endgame scaling tends to be.
Requirement: Complete 3 Challenges. This permanently adds Anvil to your item pool for future runs.
Some players report corner cases with duplicators. Treat multiple-Anvil interactions as experimental; they are not required for strong results.