A large scroched black iron helmet.

The helmet is shaped in a way that makes it look like some sort of explosive, all while still functioning as a normal helmet.
This helmet may be worn as a part of heavy armor.

The helmet contains an extremely potent magic that may be activated in the following way:

When the current wearer preforms a headbutt attack on an enemy, the magical charge in the front of the helmet is set off.
The user will then roll for 100d4 of damage.
Damage delt this way is dealt to both the user and the target and cannot be reduced in any way.
After dmg calculations are complete the user and target are both knocked back 30 ft. 

Preforming this action destroys the helmet.

Notes: Damage, Headwear