Question

i wield two blades,
flanked by justice and law.
i strike true and fair, hour by hour,
for monarchs and peasants alike.

Explanation:

This riddle describes an object with two "blades" (like clock hands), associated with justice and law (impartial timekeeping), striking true/fair hourly for all (monarchs/peasants). A clock (with hour and minute hands, or hour and second, seen as "blades") fits: it operates fairly, marking time equally for all, and the themes of justice/law can relate to time’s impartiality. The clues about two blades (hands), hourly action, and fairness for all social classes point to a clock.

Answer:

A clock (or timepiece, with its hands as "blades" of time, upholding the "justice and law" of equal time for all).