Physical Domain: Life
The domain of life controls the essence and growth of all living things within its range of influence. Life force may be strained or amplified, siphoned or redirected, and the laws governing natural life may be twisted. Characteristic vitals may change, and proliferation of all manner of life may occur in varying degrees.
This domain is represented in the leylines of Genesis and Atrophy.
Leyline of Genesis
The Leyline of Genesis carries the magics of life and vitality throughout Malkora. Wherever the leyline emerges, life surges, resulting in effects ranging from rapid overgrowth, to mass proliferation, and an abundance of megafauna.
Current emergences of this leyline include
Nimavi, where the forests have grown mighty and its beasts immense, its effect amplified by an adjacent emergence of the leyline of potency.
Leyline of Atrophy
The Leyline of Atrophy carries the magics of death and decay throughout Malkora. Wherever this leyline emerges, decay follows, resulting in effects such as withering life, proliferation of fungus and carrion crawlers, and undeath.
Current emergences of this leyline include Ba'logor, where the frozen forests of the north are known to bear the ruins of lost civilizations, teeming with unliving creatures and entities.
I really like these opposites in magic leylines! They are well named except I think that the names for the opposites of form might be a bit esoteric for most people. I had to go look them up, and I have a really large vocab. Since it sounds like you were looking for a physical form there, perhaps you were going for the ideas of solidity and malleability? That last might be too much too though? Just a thought.