Think I found the best lvl10 sword+board tank

It takes a bit to get online, but I found that a Fighter 1 > Warlock 9 creates the best all-around team player tank I've ever seen. It actively debuffs enemies, protects allies, and sustains itself extremely well.

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Overview:

Level 1: Fighter 1 > Get Protection fighting style. We will use our shield to protect ourselves and allies, get constitution saving throw proficiency, and access to martial weapons and heavy armor. For our weapon master, we want a Longsword with Sap (gives enemies disadvantage on their next attack).

Level 2 through 10: All warlock levels, choose your favorite patron

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Key Invocations:

Pact of the Blade > Use Charisma for our weapon attacks

Eldritch Smite > Knock enemies prone

Thirsting Blade > Extra Attack

Eldritch Mind > Advantage on Constitution saving throws to maintain concentration

LifeDrinker > deal extra damage and use a hit die to heal yourself (works well with our Periapt of Wound Closing)

Key Feats:

Shield Master > Push or Prone enemies, and negate damage from fireball etc.

Durable: Advantage on death saving throws, can use a hit die to heal as a bonus action

Key Spells:

Bless (from Acolyte background) > buff allies

Bane > debuff enemies

Fire shield > retaliation

Armor of Agathys > retaliation

Key Item:

Periapt of Wound Closure > stabilize when dying, and double any healing we get when we use a hit die to do so (lifedrinker, durable)

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So what we have here is a high AC tank, that can buff enemies or debuff allies and hold concentration extremely well. With the protection fighting style, we can give enemies disadvantage on attacking an ally until our next turn. We can also use our shield push enemies away from our allies, letting them move without provoking opportunity attacks.

When we do get attacked, enemies will need to deal with our armor of agathys and fire shield, they'll receive ~25 points of damage when they hit us.

Finally, we can sustain ourselves extremely well. With our periapt of wound closure, death saving throws are a non-issue, and any healing we get from using a hit die is doubled. We can use a hit die to heal using a bonus action from our Durable feat, and our Lifedrinker invocation lets us attack an enemy, deal extra damage, and heal for a hit die plus our CON modifier, and this is doubled. My only wish is that we had access to better concentration spells like haste or the like, but bless/bane on pretty much our entire team / entire enemy team is great to have.