Archimedes Armillary

Constructed by imitating the original Archimedes spheres, an Archimedes Armillary is a spellcasting focus that empowers the spell ever so slightly by refracting it through a number of conjured glass rings before the actual cast. Until attuned, the armillary is useless. 

Cast spells inside the Archimedes Armillary, and cast said spells using the next larger dice than what is required due to magnification, up to 1d12. If the dice size for the spell is already 1d12, add 1d4.

EXAMPLE - Cast Eldritch Blast and roll to hit or miss. On a hit, the target takes 1d12 damage instead of 1d10, due to the Armillary's magnification. 

EXAMPLE - Cast Witch Bolt and roll to hit or miss. On a hit, the target takes 1d12+1d4 damage, as the dice cannot be boosted above 1d12 in size. 

Archimedes Armillaries can be very easily manufactured by the employment of an artificer and the Conjure Glass Cube spell. 

Notes: (AC 14) Toss the armillary up into the air. Make a basic 1d20 roll. Once you become attuned, the armillary begins to float just above your shoulder and softly emit dim light out to 5 feet.