These are regarded as best melee spectres in game and have been for a long time, and for good reason. They have powerful basic attack with 181% more multiplier at spectre Lv.78 and 75% phys to cold conversion which can double dip with Hatred aura. On top of that they have Screech spell which increases cold dmg taken...wait but there's more: a gap closing dash-slam which triggers water geysers. They shred bosses even on a humble 6L.

My build is pretty squishy and not suited for serious bossing, by all means edit my PoB and make it tankier to suit your needs, this is just a rough template.

PoB: 6L variant 38M dmg https://pobb.in/MPkkYZWe380f

PoB: 9L variant 58M dmg https://pobb.in/aRa95kM1IMu0

https://poedb.tw/us/Primal_Crushclaw#PrimalCrushclawHarvestNessaCrabT3Spectre

Get them from blue crops in Harvest sacred grove.