Copper

Maybe a paganistic blacksmith pounded it to shape ....in fact, maybe some small humanoids may be hiding behind the shield with their spears or arrows.

Alocasia cuprea, the Copper leaf from Borneo. The aroid genus Alocasia contains many mesmerising foliage plants that would have been ideal for the landscaping trade had they not been so unpredictable. They tend to grow like perrenials - getting smaller and smaller or suddenly dying off, leaving corms in the soil for regeneration at a latter date.

This specimen has been growing for some years on a wet, shady and peaty area before reaching this size - I am pretty accustomed to it being there - hope it would not decide to die down anytime soon.