Lífþrasir

Lífþrasir (Halkeginian: Lífþrasir, "love of life") is the fourth familiar of the void. It is also called the "Heart of God".

In the anime, Saito became Lífþrasir when Tiffania summoned him as her familiar.

Name
Lífþrasir is named after Lífþrasir from Norse mythology, one of two humans who will survive Ragnarök.