Earthrune Staff is the 88th most-used weapon under the current filters (0.3% of 533,711 recorded fights), winning 40.0% overall - 8.1% of its wins come against better-geared opponents.
Best against Hallowfall (93.0%), Incubus Mace (60.0%), Polehammer (59.1%). Struggles against Demonfang (9.5%), Spiked Gauntlets (10.0%), Energy Shaper (15.4%).
Winrate by IP difference (50-IP buckets, dot size = sample size). A flat curve means the weapon carries regardless of gear; a steep one means it only wins when out-gearing.
