The Hunter Exotic Calibans Hand makes the Aspect "Knock ´em down"´s last line of abilities not work anymore. Throwing Knife kills while radiant should return back melee energy. If you have the proximity knife equipped both parts of the knife (impact + explosion) return the melee energy on kill.
If you have Caliban´s Hand equipped this does not work anymore and you will loose your melee energy completely.
The other problem is that in the exotic perk description it says: "[...] ignites the target on direct hit", which it clearly does not. It only seems to apply scorch.
This makes this exotic way worse than Young Ahamkhara´s Spine and it´s a shame
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Its really a shame though. The scorch and explosive damage from it is really good. I think this happens because the game thinks the explosion from Caliban's Hand counts as just that, normal explosive/scorch damage instead of melee.