The original five giant gods.
Firstborn
Ichika (who likely had birthrights to the crown),
Nika the chaotic secondborn (who took to the seas in search of freedom),
Sanka (who was ostracized and set aside by his family because too weak, like Sanji by Judge), and the (archetypical dumb) twins
Yonka &
Goka Yonka 2.
IMO, if Luffy has the DF of the second god, and
IF Oda follows this pattern, then either:
a) Loki is the "Sanka" of the arc, whom Luffy will help against his tyrannical family;
or
b) Loki has already obtained the DF destined to "Ichika" the rightful heir, and will 100% occupy the villain role of the arc;
or, the curveball,
c) Loki & Hajrudin both represent the dumb twins Yonka & Yonka 2, and the main conflict will come from the yet-unintroduced first- and third-born Ichika & Sanka
So far, Loki appeared to be troll-ish and manipulative enough where he could be a foil to Sanji, Mr. Prince persona included. It'd be cool if the Elbaf lore were an inversion of the Vinsmokes', having all the other siblings leave/die and only Sanji/Loki stay with Judge/Harald (and killing his dad for power > emotions, the opposite of Sanji).