Yuri wrestling for everyone.
A celestial mage can summon the king of summons for the price of breaking a key.
I don't remember what exactly but Lucy was neck deep in shit and had no other option than breaking the acuarius key.
Aquarius was never dead, her key just broke making it impossible for Lucy to summon her whenever she wanted.
Aquarius probably came through her own power, like Leo does sometimes.
Not that this makes the writing any better.
Another hot girl joins Lucy's harem and we've already seen the next girl to join Erza's good, good. This story is shit but it has great fapbait, too bad there are no porn whatsoever taking advantage of this not even yuri porn
She was up against 2 Tartaros Demons and Lamy, and her friends were kinda petrified inside the walls and floors of the enemy base. She was barely holding on by using 3 Spirits simultaneously. So it was either break the key and summon the King, or die either by getting directly murdered or by overexerting herself with multiple Spirits being summoned.