Valknut pendant, stainless steel

The three intertwined triangles of the Valknut symbolize the structure of the Germanic cosmos. The triangles embody the three realms of Asgard (world of the gods), Midgard (world of humans), and Utgard (the underworld). The nine corners represent the nine worlds: Asgard, Midgard, Hel, Jotunheim, Ljosalfheim, Muspelheim, Vanaheim, Svartalfheim, and Niflheim.
Furthermore, the Valknut is also a sign of fate. Like the three Norns, it stands for the past, the present, and the future.
Historically, the Valknut is evidenced, for example, by the Tängelgårda image stone from the 7th century. The Valknut is also depicted on the Stora Hammar runestone.

The guardian of the river Gjöll (river of death) is Móðguðr; she stands on the Gjallarbrú bridge, which leads into the realm of the dead, Hel.
The name Móðguðr is composed of the Old Norse noun "móðr" (ecstasy/rage/enthusiasm) and the suffix "guðr" (goddess).
Móðguðr is thus a goddess of ecstasy, just as Odin is the god of death and the god of ecstasy. The ferryman at the river could also be Odin, acting as a companion on the journey to the afterlife.

Many image stones and fragments convey the religious history of Norse mythology. It will certainly take decades of scientific work, if it is even possible at all, to get a clear picture of everything.

The Midgard Serpent "Jörmungandr", known from the Edda: Thor's fishing trip. Thor baited the Midgard Serpent with an ox head.
Just as he is about to slay it with his hammer, the fearful giant Hymir cuts the line.