The Vilna Gaon (the Gra)

The towering Talmudist of Vilna — and, less famously, a profound kabbalist who annotated Sefer Yetzirah, the Zohar, and Sifra di-Tzeniuta. Fierce opponent of Hasidism (he signed the bans), not of Kabbalah: his lineage carried a sober, text-critical mysticism into the Lithuanian yeshiva world, surfacing later in Elyashiv's Leshem. Proof the Tree grows in cold climates too.