Ahem, this is actually intended. This is the Final Discharge attack that all swords have. Bolt Caster can do this anytime it wants, however, just as the sword is about to run out of energy, you may discharge the blade. This isn't a secret or a cheat, and I was sure it was common knowledge. Bolt Cast takes 5 energy to use, and allows for 16 Casts. It will have one energy remaining for a Discharge Blade ability. Raze Lighter takes 5 energy to use, and allows for 16 uppercuts. It will have one energy remaining for a Discharge Blade ability. Dark Drink takes 5 energy to use, and allows 16 AoE Spins. It will have one energy remaining for a Discharge Blade. Should the Threshold be beneath 5, you can use Discharge Blade. So, there you go. Nothing secret.