Polearm Sentinel (5e Optimized Character Build)
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Ever wanted to take full advantage of your reaction actions in combat... at reach? Try this out!
This is a pure fighter build. Advancement is steady so it should be fun at all levels.
Here is the idea... use Polearm Master and Sentinel feats to maximum effect, using the oft-unused reaction "action".
Go with Str 15, Dex 12, Con 15, Int 8, Wis 9, Cha 12.
Your choice here, for flavor and for handy skills. I went with Soldier, as it fit with my concept of a Lords Alliance soldier sent to protect an important agent but feel free to select anything that fits with your own character concept. If it sounds like fun, pick it!
While there are other options the Variant Human is best, in my opinion, for the early feat selection. For your two +1's, add one to Str and one to Con taking them both to very respectable 16s at 1st level! For your feat, pick either Polearm Master or Sentinel. Both give good tactical fun in combat situations. I went with Polearm Master first for the extra bonus 1d4 bludgeon attack and the use of your reaction at 10' reach at 1st level For another option, Bubear will add another 5ft of reach to this build due to their Long-Limbed ability.
The main thing you need is a reach weapon, like a Halberd/Glaive/Pike as well as the best heavy armor you can afford (upgrade as soon as you're able to as you level and acquire more gold). I also picked up a whip and a quarterstaff, feel free to select a range weapon of your choice as well.
Now we get to the fun stuff.
Fighter 1 - You get plenty of HP, as well as a fighting style and second wind. Second Wind is as good as a healing potion, if not better (and it is definitely better as you level up). For your fighting style, pick Great Weapon Fighting. Now you get to re-roll those pesky 1's and 2's.
Fighter 2 - You get an action surge. This lets you make an extra action once between short rests. This build leans heavily on short rests... the more you take the more carnage you can dish out!
Fighter 3 - Take Battle Master. You get superiority dice, which give you 3 Maneuvers (essentially spells for fighters). Take Pushing Attack (Str save or pushed up to 15' away from you and adds 1d8 to damage), Lunging Attack (increases your reach to 15' and adds 1d8 to damage) as well as a couple others I like Menacing Attack (adds 1d8 damage and potentially frightens the target) which is handy but works against the purpose of the build by keeping enemies outside of your reach. Maneuvering Attack is another good tactical fun choice. You now get 4 uses of your Superiority Dice between short rests, again the more short rests you take the more fun tricks you can pull off.
...and it gets better.
Fighter 4 - Here is where you get both feats kicking in and the REAL fun begins! Take Sentinel which stops enemies in their tracks when they enter your reach, using your reaction. It also gives you opportunity attacks on Disengage, so pesky casters can't get away from you without taking some much needed punishment. Lastly, it also lets you spend your reaction to defend an ally by attacking one of their attackers (within reach). Lots of reaction goodness kicking in now!
Fighter 5 - Extra attack. You get an entire extra attack, with Action Surge that's 4 attacks with your bonus polearm bludgeon attack. With the proficiency bump, you now have +6 to attack rolls, for 1d10 + 3 damage plus any Superiority Dice used in those 4 attacks. You should also have Plate by now, if not earlier, for a respectable AC of 18!
Fighter 6 - Ability Score Improvement. Add 2 to your Str, for 18 Strength and a Maneuver DC of 15. Your attack roll bonus is +7, your damage is 1d10 + 4. Slash, Bash, Slash! ...every round!
Fighter 7 - Extra Superiority Die, two more Maneuvers. I advise Trip Attack and Disarming Attack. Combining a Disarm Attack & a Push Attack outside of your reach leaves an opponent in a very bad place!
Fighter 8 - Ability Score Improvement. Add 2 to your Str, for max 20 Strength and a Maneuver DC of 16. Alternatively you can take the Great Weapon Master feat. This gives you +10 to damage with a cost of -5 on the attack roll, a 25% additional miss chance. That damage sounds great, I know, but the miss chance works against the purpose of the build so I advise caution in this selection. If you have "Hot Dice" then go for it!
Fighter 9 - Indomitable. You get to re-roll a saving throw once between long rests. Your proficiency bonus bumps by one, so your normal attack roll bonus is +9 and your Maneuver DC is now 17! ...or 16 if you went with Great Weapon Master.
Fighter 10 - Two more Maneuvers, and your Superiority Dice are now d10s. Pick whichever Maneuvers you'd like.
For any extra feats, I'd advise Mage Slayer (reaction on someone casting a spell in reach, giving disadvantage on their concentration check, if any), Savage Attacker (re-roll one weapon attack damage per turn) and/or Martial Adept (yet another Superiority Die, d6, and two more Maneuvers).
Also the Resilient feat on Wisdom saves to make it an even number and giving you proficiency in the most common mental save stat is big (you can’t do damage if you are feared, held, mind controlled etc for multiple turns).
Or you can put 18 levels in fighter cavalier and get a reaction for each turn of combat
As mentioned earlier Disarm Attack & Pushing Attack can be a very effective combo. In general Pushing Attack plus effective use of your reach & Sentinel reaction can keep at least one melee opponent frustrated. This build can benefit greatly from synergy with other classes. Maneuvering Attack can get your rogue into a sweet spot and still leave their full movement and bonus disengage for impressive battle mobility. Other allies can benefit from that trick as well but sadly won't have that handy bonus disengage. You can increase the effectiveness of a caster capable of casting a lasting area affect spell by using Pushing Attack or your Sentinel reaction keeping them in the area of effect. Lots of other synergy opportunities with this build.
Tactical fun, for sure!
Heres hoping you enjoy it and your party enjoys it too! Oh... and your DM doesn't punish you for having such a good build!
...credit to the Machine-Gunning Crossbowman build creator, for formatting (and some overlapping content).