Bloom is one of the five affinities, the colours of power that leak into the Hallow through the imperfect Covenant. It is the affinity of growth, beasts and living ground, and Virenna, the Greenmother holds it. Its art is Greenmother's Call, which Virenna, the Greenmother teaches.
On the ring of affinities, each affinity feeds the next. Ash nourishes growth, so Pyre feeds Bloom. Growth orders itself, so Bloom feeds Lumen.
A Sealborn whose core wakes in Bloom can master its spells and reach the complex spells of Pyre and Lumen. Reverie and Umbra lie across the ring and repel it. From them, such a mage learns only the simpler spells, and casting against the grain costs more, fails more easily and lands weaker. The exact prices belong to the ruleset.
Cultivators of Bloom do not fear their neighbour in the ring. Ash is the gift the fire gives back, they say, and a field that has burned grows greener than one that never did.