Amulet of Accelerated Abjuration

This enchanted amulet allows the user to cast spells of the Abjuration school much faster than normal.  A spell with the casting time of more than an hour may be reduced to 1 hour, and any spell with the casting time of an hour or less may be reduced to 1 action. 

This item may be used many times per day, however the temporal shifting of spell acceleration is very hard on the caster.  If used more than once per long rest, each use after the first forces the caster to make a DC 23 Con saving throw and take a point of exhaustion on a failure.