Here’s the foot route in OSRS: complete Children of the Sun , go to Civitas illa Fortis, then run east out of the city and follow the main path into the Tlati Rainforest toward the mining area. When you reach a cave entrance near the mines, go inside to be sent directly to the Gemstone Crab’s current spot.

If you do not see the crab on the surface, that is normal, because the cave is the shortcut to its active location. One guide also notes the path is safe enough to run even at low combat levels, with only some slow-moving jungle creatures along the way.

Simple route

  1. Finish Children of the Sun.
  1. Go to Civitas illa Fortis.
  1. Run out through the eastern side and follow the dirt path northeast into the rainforest.
  1. Enter any mine cave near the trail.
  1. You will be taken to the crab’s current location.

Notes

  • You do not need to complete Twilight Promise just to get there on foot.
  • The cave system acts like a moving teleport to wherever the crab is currently spawning.
  • If you have started Twilight Promise, there may be faster travel options, but walking works fine.

TL;DR: finish Children of the Sun , run east from Civitas illa Fortis into the rainforest, and enter the cave near the mines to reach the Gemstone Crab.