Инверсия
Never have I seen…
После отрицательных наречий в начале предложения — порядок как в вопросе:
- Never have I seen such beauty.
- Hardly had he come in when everybody fell silent.
- Only then did I realise my mistake.
- Условие без if: Had I known, I would have come. Should anything happen, call me.
So do I / Neither do I — «я тоже / я тоже нет».