"Darkness."
Tyler's mana surged forth, and immediately, absolute darkness spread from a point next to Rain. This spell was originally a Tier 1 spell that would only fill a 15-foot-radius sphere with magical darkness for a duration of 15 minutes.
However, with the sheer amount of mana the spell had consumed from him, he could sense that its range had massively increased, almost covering the entire hall.
The darkness was pure. Even a creature with Darkvision would be unable to see through it, and nonmagical light would be unable to illuminate it. Rain, being a dark elf, naturally possessed the racial trait of Darkvision.
Originally, she had wanted to continue her pursuit using her Darkvision, but when she noticed that it couldn't penetrate the darkness, she halted her steps and took a defensive stance without hesitation.