A Sword Called Honor

Honor.

Honor's sentience is provided by the essence of a Marut.  As such, Honor has rather strict definitions of what is, and more importantly, what isn't, honorable behavior. Wielders that are honorable by its definition gain all sorts of benefits, while those that act in a dishonorable fashion suffer penalties.

Presume the LEGO person is 6 feet (about 2 meters) tall.

Its hilt is wrapped with unicorn-leather and the weapon itself is forged from a magical alloy of moonsilver, cold iron, orichalcum, mithril, heartwood, onyx, and steel, Honor can slice through all material-based resistances, presuming it connects, of course.  To assist in this endeavor, honorable wielders using Honor as their weapon gain Advantage on attacks.

In addition to Advantage on attacks, critical hits trigger a Thunderwave spell upon the target.

Honor also provides access to several abilities stemming from its Marut essence: Air Walk, Dimension Door, Locate Creature, True Seeing, and Plane Shift.  While the sword's wielder can activate these abilities, Honor will also use them in pursuit of the 'honorable' solution, or to prevent a dishonorable situation.

Below are some ideas regarding Honor's thinking.

Examples of what Honor considers honorable behavior:

• accepting a challenge to a one-on-one duel
• issuing a challenge for a one-on-one duel
• sacrificing self for others, typically via combat
• announcing oneself before attacking
• making a promise, vow, or taking an oath
• keeping a promise, vow, or oath
• accepting the surrender of enemies

Examples of what Honor considers dishonorable behavior:

• surrendering to save one's own life
• not accepting a challenge to a one-on-one duel
• murdering prisoners that had surrendered
• murdering beings that cannot defend themselves
• putting self before others
• not attempting to rescue comrades-in-arms during a battle
• retreating from a fight once started (but not avoiding a fight entirely)
• attacking from behind or from ambush
• the use of poison
• breaking a promise or vow or oath
• breaking any personal taboos (Honor knows)
• using any of Honor's abilities to leave a fight - major infraction
• using any of Honor's abilities to 'cheat' a fight - major infraction

Honor is capable of speech, but doesn't speak much.  When it does speak, it is either to answer a direct question asked of it, to warn the wielder of a potential dishonorable act, or to issue a challenge to something mighty in order to give its wielder a chance to redeem their honor.  This challenge is always in a language the mighty thing can understand - and so can the wielder.  

It always speaks in a loud, clear, emotionless voice.  Its challenges are more booming than just plain loud.

For minor infractions of dishonor, Honor's wielder attacks at Disadvantage.  For larger infractions, Honor will challenge creatures or beings to single combat, and that entire fight the wielder is at Disadvantage.  Honor may instead demand some form of service from the wielder to redeem itself.  Once redeemed in Honor's eyes, attacks are at Advantage and powers become available again.

In extreme circumstances, Honor will attempt to dominate a dishonorable wielder in order to have them go somewhere private and commit seppuku. At this point, the wielder is dead and their honor redeemed.

As such, this is how Honor is normally discovered - in the belly of a kneeling corpse or skeleton in some out of the way location. 

-----

DM Notes: Honor as a whole is a slippery concept that walks a fine line between vainglory and pride.  

For inspiration, look at real world honor-bound cultures for ideas.  

Alternatively (or additionally), there are tables in the 1e Oriental Adventures, the CMG supplement, the 3.5 SRD ruleset, Pendragon (any edition), Hackmaster, and other systems and games.  Just be sure to let the PLAYERS know what the sentient blade finds honorable and dishonorable... if they think to ask it.  If not, trial by error is a method.