The firebird spell was quite robust, but it still required a supply of mana. Especially if it were to remain for longer than intended. Normally, the bird would attack on command and rush through the mana it is composed of. Using it as a show of force was certainly not normal.
While the upkeep was not as much as a normal fire spell at its level, Eldrian still needed to feed it mana to keep it stable. At this distance, Sofiera couldn't exactly do that.
It was this mana upkeep that Levana noticed, informing her of the fact that Eldrian had somehow taken over control of the spell. A feat she knew was far more difficult than dispelling a spell, and normally only possible if the new owner was above the original caster.
Evidently, from the power of the firebird, Levana understood that this case was the opposite. She had never encountered this spell before, but the sheer quantity of mana inside it made it clear it was a Tier 7 spell.
