"Right then."
Hex took a breath, then started reading from the Grimoire. Almost immediately the air was heavy with the smell of ozone and an oppressive heaviness. A dark grey cloud erupted from thin air over the museum and roiled with pink and violet lightning within it. Similar colored sparks of energy gathered around Hex's hands and arms, arcing over her as the spell gained momentum.
At the height of the spell, a shimmering lavender energy filmed over her eyes as she sent her perceptions into the museum to spot the hostages. Thunder boomed overhead...and the cloud spat a lance of brilliant lightning downward!
The lightning sluiced through the roof of the building as if it wasn't even there, causing no damage in the process. It branched, splitting into countless dozens of arms that spread into the hostages, each one finding a single target out.
(They may make a Dodge resistance check if they wish)
Those who allow, or fail to move quickly enough to avoid, the lightning are consumed in flashes of light, and ripples of thunder reverberate through the museum!
An instant later, another bolt of lightning descends behind the police line. Those who vanished within the museum reappear there, in exactly the formation they'd been before. Only now, safe.
Hex gasps and puts a hand to her temple as the strain of the spell hits. She swallows nervously then looks up and nods.
(Going to save my HP, so 1 level of fatigue taken!)