You did

You open your needle filled maw in preparation to clash. Jadwiga charged, her holy hammer at her side. Your heavy footfalls shake the courtyard, causing loose and weak masonry to fall and shatter. It seemed to take forever, the run to the middle, but when you and her met it was clear who was about to win. She swung her hammer in a wide arc, but by then you were high in the air and she struck nothing. Jadwiga looked up with horror on her face. There was no time to move. Your body, gargantuan and horrible, blocked out the sun, and by the moment grew larger and larger until...

"Gods forgive me, for I have-" was all she managed to utter.

The courtyard cobblestones broke themselves free of their terrestrial tethers in a shock wave, the castle trembling and beginning to collapse on itself. Your body crashed into the ground, giant maw first, swallowing the King and a massive chunk of the earth in one bite. You stood there for a moment, your body struggling to swallow it all, but with a tremendous 'crunch!' you manage it. The King is dead, and with that done your purpose is almost complete. You do feel a tinge of regret however, as if a very dear person to you just died, but... it was a very small piece, a piece that was dwindling by the second like a dying candle, before disappearing completely. Now you felt completely hollow, your base animalistic desires taken over, and there was nothing left redeeming about you, as if all the infinitely small voices of good and reason that used to chatter incessantly deep below were silenced and imprisoned. Now you were nothing more than a perfect pawn for your master.

Now all that was left to do was to reduce the Capitol to rubble, which you've already made great head ways with. With no-one left to oppose you you climb on top of the castle rubble and let out a triumphant hellish roar from all your mouths for all to hear; the Dark Lord is victorious.