Functionally; the Spy's Dagger is an enhanced Rogue Dagger+, granting Defense & Resistance to Matthew and allies within 2 spaces of him for 1 turn after combat he initiates, while inflicting Defense and Resistance -6 onto his target and all other foes within 2 spaces after the fight.
If refined for it's unique effect, it grant Matthew an in-combat bonus to his Attack equal to all of the debuffs on his target.
After combat, if unit attacked, grants Def/Res
|400 SP, 500, 200|
|Grants bonus to unit's Atk equal to total penalties on foe during combat.|
| After combat, if unit attacked, grants Def/Res|
+6 to unit and allies within 2 spaces of unit for 1 turn.
After combat, if unit attacked, inflicts Def/Res-6
on target and foes within 2 spaces of target through
their next actions.