First off, lets create two new Battlemaster Maneuvers so we can bring the total to 18 maneuvers available.
1. Limb-Lock Attack. When you hit a creature with a weapon attack, you can expend one superiority die to forgo rolling damage and instead attempt to grapple the creature with your weapon. Add the superiority die to your attack roll. The result is used in place of your Strength (Athletics) check. While the creature is grappled, you use your Attack Roll in place of a Strength (Athletics) check for all contested rolls involving the grapple.
2. Harrying Attack. When you hit a creature with a weapon attack, you can expend one superiority die to harry your opponent. You add the superiority die to the damage roll. Until the start of your next turn, your opponent is considered to be one size category smaller for the purpose of adjudicating grapples, shoves, or any attack that takes size into consideration that is made by you or your allies. If your opponent is grappled before the start of your next turn, then it is considered to be one size category smaller for all contested rolls to escape the grapple as long as your opponent is within your reach.
And before I forget, here are three important rules for Item Sets:
3. 1) When you equip four items from a set, you may unlock a partial set power. In order to use this power, you must attune to it. This uses one attunement slot.
4. 2) When you equip all six items from a set, you may unlock a full set power. In order to unlock this power, you must attune to it. This uses one attunement slot.
5. 3) Minor Property: Set Exclusion. Whenever a partial or full set power is unlocked, the items in the set all gain this new property. This property causes any item worn or carried by you that belongs to a different magic item set to become dormant and inactive. Such items are considered to have no magical properties while you benefit from another set’s partial or full set powers.
This way a character wanting to gain all the benefits from a set must use up all three of her attunement slots, and so the character is only attuned to the full set of items and can’t be attuned to anything else. That, and no other items from different sets can be used, so you’re either all in with the set, or you fold.
I think fits thematically, and is appropriate from a rules and balance perspective.
So, how to organize the 18 maneuvers into groups of six…?
6. Maneuvers that involve allies:
Commander’s Strike, Distracting Strike, Maneuvering Attack, Limb-Lock Attack, Harrying Attack, Rally,
7. Maneuvers that are flashy:
Disarming Attack, Evasive Footwork, Feinting Attack, Lunging Attack, Parry, Riposte,
8. Maneuvers where you still hit someone on the head:
Goading Attack, Menacing Attack, Sweeping Attack, Precision Attack, Pushing Attack, Trip Attack
That works. One group of maneuvers is about being the battle boss on the field. The second is kind of a flashy sort of Three Musketeers type of group. And the last group is all about kick, bite, chop, punch, slash, stab, teabag-with-your-spiked-codpiece-for-damage.
The kicker will be making magic items. It should be easy to write up the magic items, but each item in a set–as well as the set itself–ought to have Realmslore wrapped around it like a nice bow that’s just waiting to be untied. This means writing something that appeals to players running Battlemasters as well as to DMs in need of good adventure hooks and good ideas to wrap around a quest to complete an item set.
If you take care of the DM, the players will follow (or something like that).
So, what do I need to figure out still?
9. How rare should items in a set be? An assembled set ought to be right up there with Legendary magic items (or possibly artifacts). On the other hand, it’s no fun to have just one or two set items early on and not see another one until several levels later. Maybe that’s where your idea for Partial Set Powers comes in: A player can unlock a partial power and enjoy that for the next five levels and find one more set item in that time, and then find the last item around 17th level or so and completing the set/becoming a juggernaut of superiority dice.
10. Should I be giving advice to the DM on how sets affect a campaign? (The closest experience I have is with PC Paladins hunting for Holy Avengers, and I wasn’t very nice about it. Oh dear…)