Alex understood a few things after talking to Andre; his curse was something that needed to be suppressed. Someone who was responsible for the Curse's origination was the one who gave Solaris the orders to seal the Curse.
However, since Solaris and his people were involved in a war, they used the Curse—the Devourer, for their benefit. After all, the Curse has the ability to not only instantly cease the existence of a being by consuming their grimoire, but also adopt a fragment of their powers.
And until the Curse continued to eat, its hunger and strength continued to grow.
Once the war was settled, Solaris deemed that the Curse had absorbed more than necessary and its hunger might now harm the Gods. As such, they followed the original orders and sealed the curse, and suppressed its powers.
