Speculation

Ignoring Dilitrio's outburst, Kyran launched a sudden attack. His target was not Dilitrio, who was retreating to gain distance, but the floor beneath them.

BAM!

The floor exploded, creating a crater almost the same size as Dilitrio's Area magic.

Kyran did not destroy the arena to counter Dilitrio's Area magic or to increase the low visibility. The additional cloud of smoke and commotion would not affect the senses of the dragons watching from the audience or the hovering platforms. Instead, he destroyed the arena so he could force Dilitrio back while he prepared a surefire move to force everyone's gaze away from the arena.

With Dilitrio's poison negating Kyran's use of Draconic magic, he could not use it. Thus, instinctively,

Kyran used the Void mainly because it was the magic that could easily counter the poison's effect. However, that was not the only magic at his disposal.