Silk is found in the Coral Cave. To get in you need a Coral Key ( found by killing crabs or fishing
), when inside Coral Cave. LvL 2 crabs are waiting but there is also Silk Crabs ( LvL 15 ), They are neutral mobs. Silk Crabs drop Silk but Rarely so prepare time for a grind. ( " I would say killing 10 Silk crabs will get you maybe 2 Silk. GLHF Grinding." )

--SneakpeekTV (talk) 21:16, July 16, 2018 (UTC)

" The Red Crab (level 50) at the end of the Coral Caves also drops around 10 silk occasionally as well. If you have the levels to kill it then it's a much quicker way to get silk. " -Cullen

As of update 127 spiders also has a small chance to drop silk.