Mana Regen

Mana Regen here is the Rift stat: it makes your Mana come back faster while you are in the Rift, starting from a base of 0.¹ It is the same stat as Rift Mana Regen; some Rift items (such as the Rift Necklace) write it as plain "Mana Regen" in their lore, which is why it has its own page.² Mana regeneration outside the Rift is a different thing, handled by Mana itself.¹