D&D 5E Eldringht Knight using Polearm (Glaive/Halbert)

[WookieCutie]

Hello, everyone! I apologize if this has been discussed before, but I couldn't find information specific to what I've had in mind.

I've conceptualized a glaive-wielding EK. The DM will allow for Variant Human, so I could start with a feat. Looking around in forums, there seems to be some dissonance on how Polearm Master (PAM) and War Caster (WC) work (+/- the Spell Sniper (SS) feat).
From my interpretation: if I have both
PAM [While you are wielding a glaive, halberd, pike, or quarterstaff, other creatures provoke an opportunity attack from you when they enter your reach.]
and WC [When a hostile creature’s movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only that creature.]
I should be able to use a cantrip as my opportunity attack (OA).
However, booming blade and green-flame blade are 5ft spells, so I couldn't reach them with my 10 ft reach weapon.
That is where SS [When you cast a spell that requires you to make an attack roll, the spell’s range is doubled.] comes in. Not only does it apply on OA, but it also allows me to cast these cantrips from 10 ft away when I normally attack.

From a ruling point of view, is this allowed/possible?

From a damage point of view, I will not be able to us PAM bonus attack when I use the cantrips until Level 7 where EK gets War Magic.
However, I will also be losing the Extra Attack feature since I will not be able to attack twice when using a cantrip. Then scaling past level 10, I will lose another Extra Attack.

From a damage point of view, #
a.) have I understood something wrong is terms of how Extra Attack and War Magic work
b.) Other than thematically, does it make sense to use 3 feats for what appears to be a less than synergistic character.

Thank you for taking the time to read this block of text and reply.

 

[DND_Reborn]

It seems like you have it right for the most part. The only things I would clarify is:

When you use the cantrips to make your OA, that uses your reaction. This has nothing to do with what you can do on your turn with your attacks/ bonus action.

So, you can use the PAM bonus attack without War Magic.
You can use the Extra Attack feature normally regardless of if you used one of the cantrips as part of the PAM OA reaction attack.

Also, since you are only use SS to gain the double range feature, your DM might allow you to use the cantrips without it. The 5 feet reach limit IMO is based on the limit most melee weapons have and might have been an oversight since some weapons have a reach of 10 feet.

Also, you might want to consider Lightning Lure, since it has a range of 15 feet and would work without the Spell Sniper feat.

Finally, just to mention you don't need WC in order to cast spells even though you have a two-handed weapon since nothing in 5E assumes your weapon is being held in both hand during the entire round.

 

[WookieCutie]

Thank you for the reply! It does help with making some sense from the interaction between feats.

My main question however stills remains:
is it worth giving up the extra attack (from fighter) for war magic? (presumably yes?)
And is it worth it giving up 3 ASI/Feats just for the above interaction, in terms of damage and resources?

 

[DND_Reborn]

Well, not only are you not taking the attack action (and thus not benefiting from extra attack), but you lose the bonus action feature of PAM because you are using the bonus action from War Magic...

I see PAM only really useful in forcing the foe to engage and gaining the OA.

War Caster is more useful IMO because allowing you to cast a spell as a reaction for the OA. With something like Lightning Lure, this could be fun if a target tries to flee, provokes an OA, and you use the cantrip to pull them back into you!

And, of course having advantage on concentration checks via War Caster is really good.

It is a hefty investment and off-hand I think you could accomplish something like what you want without all the investment. The difficult thing will be action management. With only one reaction and one bonus action, you'll find a lot of things potentially competing for those. For instance, if you use your reaction for an OA, you can't use it for Shield. Both War Magic and PAM want to use your bonus action, etc.

In terms of damage, I think a better feat would be GWM, although part of it will also compete for the bonus action. Also, it might seem like a weak choice, but the Paladin in our party with Resilient (DEX) and Shield Master LOVES it because he was able to take no damage from a 3 lightning bolts last night when he made all three saves. Without the feats, it would have been much different.

So, a lot depends on whether it is worth it to you or not? I could see a really cool PAM Eldritch Knight build with War Caster, etc. Even Spell Sniper has its uses which can be really good. A better question for your EK is how do you want to use your spells? For direct attack, defense, or to augment your abilities? That will determine a lot IMO.

 

[Shiroiken]

The EK doesn't benefit from PAM very much at all. Your combo, while it does work, is a HUGE feat investment for a subclass with 3 focused abilities (Str/Dex, Int, Con). A non-EK can preform the same benefit simply by taking PAM and Sentinel. The EK wants to use the cantrip whenever it's more efficient, but giving up the bonus action attack just isn't worth it unless you need non-weapon damage. Once you have War Caster, you don't even need PAM for the bonus action attack, because you'll just make a regular weapon attack instead.