Grandmaster

Hours upon hours are spent mastering the aspects of a game. Days upon days are spent mastering the aspects of battle. But it takes true time and dedication to bring the skills of a game into the battlefield. And that is exactly what Grandmaster Fighters intend to master, proving their potential bot on the board and the battlefield.

Material Advantage

Starting when you choose this archetype at 3rd level, you gain a total of 15 Material Points that you can use to produce varying effects. You regain the usage of your Material Points after a Long Rest. You can use Material Points to produce any of the following effects:

King's Gambit. When you roll initiative, you can expend one Material Point to gain a +5 bonus to the roll, but the first attack made against you in combat has advantage.
Lion Defense. When you roll initiative, you can expend a Material Point to gain a +5 bonus to your AC until the end of the first round of combat.
Durkin Opening. When you roll Initiative, you can expend a Material Point to forfeit your first turn, and one of your ally within 60 feet of you can take an additional turn at your initiative count. 

Additionally, you gain proficiency with a gaming set.

Material Effects

You can use Material Points to cause a lasting effect on yourself. When you roll initiative, and as a Bonus Action on your turn, you can expend Material Points to gain a Material Effect, which lasts until you die, fall unconscious, or use a Material Effect again. You can also end the effect as a Bonus Action and it automatically ends when combat ends.

Tactics

At 7th level, whenever you have a Material Effect active, you gain an additional benefit depending on the effect.

En Passant. When your Pawn effect is active, you make two attacks whenever you make an Opportunity Attack.
Fork. When your Knight effect is active, your first attack on your turn is an automatic hit if there are more than two hostile creatures within 30 feet of you.
Battery. When your Bishop Effect is active, allies within 15 feet of you have advantage on all saving throws and the first weapon attack on each of their turns.
Castle. When your Rook effect is active, all allies within 30 feet of you gain half cover until the start of your next turn whenever you dodge or dash.
Wayward. When your Queen effect is active, you have an extra turn on the first round of combat. The extra turn is taken at initiative count 20, winning initiative ties.

Strategic Thinking

At 10th level, you gain proficiency with Intelligence saving throws. You gain proficiency with another gaming set.

Fried Liver

At 15th level, you learn to sacrifice some defence in exchange for offense. When you take damage, you can use your reaction and expend two Material Points to gain vulnerability to that instance of damage, which cannot be reduced or negated. The creature that damaged you then gains vulnerability to the next instance of damage they take within the next minute.

Brilliancies

At 18th level, each of your Material Effects have an extra effect while they are active.

Promote. When your Pawn effect is active and you score a critical hit, you can instantly swap to any other Material Effect at half the Material Point cost (rounded up).
Royal Fork. When your Knight effect is active, using your 7th level Fork ability gives you 10 temporary hit points until the start of your next turn.
Boden's Mate. When your Bishop effect is active, you and every ally within 15 feet of you gain immunity to damage from ranged attacks.
Lane Control. When your Rook effect is active, your ranged weapon attacks target every creature in a line that is either the long range of your weapon or 100 feet- whichever is longer. You can dodge as a Bonus Action.
Queen's Gambit. While your Queen effect is active, whenever an attack misses you, you gain immunity to the next instance of damage you take.