What Selena just did was similar to what Mia had done at the warehouse when they went to clear out those ants, gathering the energy of an element for a long time without casting any spells.
This would lead to the manifestation of the element, and depending on the strength of the mage, the manifestation might become something more powerful than spells or just a showcase of the element.
This was the case difference between Mia and Selena. Selena was at the Expert rank so when she manifested the energy of the water element, it had become a massive body of water that could very well flood a street. Had a weaker mage tried it, the outcome might have been a small puddle at best.
In Selena's case, she was at the Core rank and had only created a show of a lightning bolt with her manifestation. This was why it had vanished briefly after appearing and didn't touch the ground.
If a stronger mage had tried it, the outcome might have been stronger than even the lightning bolt spell!
