Day 4 - D is for Death Whistle.
Additionally, Aztec warriors would blow this device while running into battle - the unnerving scream of the whistle meant to disorient and sow fear into enemy ranks. A single whistle is demonstrated below, with a synthesized mass of whistles at the end of the video:
Enchanted with the aura of death absorbed from the pain and suffering of sacrificial victims, these whistles have distilled fear within them...
A blast from this whistle may cause fear 1d4 times per day. When used en masse, each additional whistle will penalize saving throws vs fear by -1.
Because of the whistle's occasional association with wind gods, 1 in 4 whistles will also be able to cause a wind gust once per day, knocking down small creatures, blowing out light sources, blinding and disrupting foes, and negating missile attacks.