Which mythological protective product was famously marketed as being 'dipped in the river Styx' to create brand differentiation?

Throughout history, cultures worldwide created talismans, amulets, and charms as some of the earliest 'consumer products' with specific brand identities and perceived benefits. These mythological items were often marketed through oral tradition, with distinct packaging elements and 'customer testimonials' from heroes and gods. Test your knowledge about these ancient product innovations that bridged the mortal and divine realms!

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Achilles' armor
Perseus' reflective shield
Hermes' winged sandals
Thor's hammer Mjölnir