Judgment Scythe
From Chrono Wiki, a database for the Chrono series that anyone can edit
"A scythe that renders but one judgment: guilty"
Magus' 4th weapon can be found in the Lost Sanctum.(Prehistory) It has and attack power of 155 and can be sold for 18,000 G. It has the power to inflict stop on enemies. It is only found in the DS version.