They moved at the same time.
To call their motions themselves attacks was wrong, because with the speed and power imbued in them, even a regular mortal would be able to dodge.
However, the intent behind them was to kill, nothing more and nothing less.
The Soul Emperor raised his withered arm and placed his finger on Tiamat's forehead, while Tiamat did the same for him.
And the attacks they prepared were unleashed directly onto the Divinity of their opponent.
Tiamat frowned as she felt it.
The Soul Emperor also used those ten steps to judge what the root of her Divinity was, the truth behind True Death.
The conclusion he came to was far more complex than hers.
Tiamat was born in that kind of place.
A place devoid of anything, where only she existed.
She walked a lonely road from that point. Everything she ever cherished was taken away from her by death, and at some point, even her psyche was consumed by the concept.