On pagan deities.
Eastern Slavs had certain Iranic deities. Sеmargl and Khors in Kiev’s pantheon are Iranic in origin. I don’t think these deities existed in other Slavic countries. Not even in Belarus. On the other hand there are similar deities in Baltic mythology such as Perkunas in Lithuania and Perkons in Latvia . Perun in Slavic countries. Vels in Latvia, Veliona in Lithuana. Veles in Slavic countries. Mara in Slavic countries and Latvia. As well as various spirits.