Deep Magic for 5th Edition, pocket edition.
From the publisher-
Our kobold minions have traveled the planes, seeking the secrets of magic: unearthing ancient tomes of forgotten civilizations, bargaining with demons and creatures of the void, and scaling the towers of shadow fey mages.
Now they pass along their hard-won knowledge to you in DEEP MAGIC, an arcane series for 5th edition! Here you’ll find new schools of magic, arcane traditions, new and variant spells, magical feats, spell-slinging NPCs, and more.