Duke

Duke never had a drop rate, because it is a developer-exclusive aura that has since been removed. The Sol's RNG Wiki gives it the Unobtainable tier and credits 53_Axis. It was added on November 30th, 2024 in Eon 1-1, but the community only saw it during the content creator event on January 24th, 2025.

The effect is minimal: green circles pop up around the player in a random-looking order, and the aura does not display a name when equipped. It was the first aura without a title, with pukeko and Nothing following later. The wiki says the design is based on Duke Erisia from the game Deepwoken, which also explains why the inventory entry reads "Duke Erisia", and that despite having a single effect it can be quite laggy for reasons nobody has explained.

No luck value, biome or event applies here, and the data provides no in-game description. For anyone comparing rare listings, it belongs with the removed or staff-only entries rather than with the aura you can chase through rolling.