D&D 5E (2014) Point me to the rule please:

[Minsc]

I'm trying to find the errata/ruling that says you can't use an eldritch blast as your reaction attack when using the polearm master feat.

Thanks.

 

[Jester David]

I assume you mean the second bullet point to the effect of "While you are wielding a polearm creatures provoke an opportunity attack from you when they enter your reach."

It's not stated that the opportunity attack has to be the polearm, but you are expected to be wielding the two-handed weapon, so you cannot make use of a spell that has Somatic or Material components. If you attack with another weapon or ability, you're no longer really wielding the polearm.
And the narrative of the power is using the polearm to make the attack. So it's fair for the DM to rule that you cannot attack with another weapon.

Besides that, eldritch blast takes 1 action to cast, not 1 reaction, so I don't believe it can be used to make an opportunity attack. The opportunity attack section says an attack needs to be a melee attack, not a ranged attack or spell attack.

 

[pukunui]

Besides that, eldritch blast takes 1 action to cast, not 1 reaction, so I don't believe it can be used to make an opportunity attack. The opportunity attack section says an attack needs to be a melee attack, not a ranged attack or spell attack.

Yeah, you need the War Caster feat in order to be able to cast a spell as an opp attack.

 

[Lidgar]

Furthermore, reactions triggered by opportunity attacks are melee attacks, not spell attacks:

To make the opportunity attack, you use your reaction to make one melee attack against the provoking creature. The attack occurs right before the creature leaves your reach.

EDIT: D'oh, already said above.

 

[amerigoV]

Its over there (points)

 

[Jester David]

Forgot about War Caster.
With that feat and Polearm Master, it should be possible to eldritch blast as an Opportunity Attack. RAW anyway. Your DM might overrule, saying you need to use the polearm to attack with the Polearm Mastery feat.

I'd allow it. It does better damage than a standard polearm attack, but it takes two feat and requires the squishish warlock to get up into melee range.

 

[Lidgar]

I agree with JC - would allow it if they went through the trouble of getting both feats. Plus, pretty cool thematic.

 

[Sage Genesis]

While not an official rule, Mike Mearls did say that you can't combine Polearm Master and War Caster this way.
http://www.sageadvice.eu/2014/09/16/polearm-caster/

 

[everyman322]

Jeremy Crawford posted a similar tweet, but IMO it doesn't seem consistent with Crawford's Sage Advice: Feats article, which says Crossbow Expert's second benefit works with ranged spell attacks, and Great Weapon Master's first benefit works with non-great weapons.

And should feats not work together? For example, would you rule that Sharpshooter couldn't be used on the bonus attack from Crossbow Expert? Should Lucky not be usable on any roll related to another feat?

 

[Celebros]

I'm very surprised Mike/Jeremy both went this direction regarding Polearm Master and War Caster, particularly in light of the way most 5E rules are interpreted (as simply/straightforward as possible).

This forces me to retool a character I have made to join a fifth level campaign next month, as I was going Fighter/Bard and was planning on playing a cocky character who would often make use of Vicious Mockery as his Opportunity Attack (both effective and fluffy). Alas. I may petition the DM to see if he will allow it anyway or perhaps put a limitation on the types of spells which could be used.