I got the solution thanks to " JVC " on the steam forum.
You need to go on the second world Ealam, south east of the capital you'll find Harefoot farm and in this location you'll see a big rock on the right side, near this rock you'll find a rabbit leg. Bring this rabbit leg to the Lepus Regina Grove in Otam ( south east of the map) and when you go near the ruins , the Lepus Regina will appear. You kil it to get the achieve.