Grasp of Hadar with War Caster/Opportunity Attack

[Beamer92]

Grasp of Hadar States:


Once on each of your turns when you hit a creature with your Eldritch Blast, you can move that creature in a straight line 10 feet closer to yourself.

Which for my scenario is a little unclear. Let's say I'm a Hexblade-Pact of the Blade that casts Eldritch blast to pull some smug little Saytr off his perch, then I use my movement to close with him and get ready to beat the heck out of him with my Pact Weapon.

Now on his turn he chooses to move away, provoking an attack of opportunity. With Warcaster I can cast Eldritch Blast instead of attacking (not that I should, but I CAN). So my question would be, can I pull him back 10ft closer with Grasp of Hadar on the AoO? With RAW I would say No since it is not my turn.

But this case feels like it wouldn't have been the intended situation for RAW. I also kind of feel like the whole point of warcaster would be to use my spell and all of its features instead of slashing for whatever reason (maybe I don't want him to get where he intends to run to, or maybe I just don't wanna follow him there). So in the event that I chose to use Eldritch Blast instead of the more powerful melee attack, it would be to benefit from my eldritch invocations. So as a DM, I might say its ok since it doesn't appear to break anything and gives more versatility/fun to my chosen invocations. (This might have bigger implications for higher levels/invocations so that's more of my concern, it's my first warlock and he's lvl 3).

I'm clearly not min/maxing this guy for damage output. I'd rather him be calculating and versatile, and sometimes I wanna be a controller more than a DPS. So I'm curious as to other people's thoughts before I discuss it with the DM. He'd probably let it go and not care but as a DM myself I do care.

[Man_Over_Game]

Technically, you would not be able to. It's the same reason a Cleric can't use their divine strike features out of turn when Rogues can.

There's another reason you can't, though. Opportunity Attacks occur BEFORE the enemy moves away from you. They'd still be in the same square that they'd try to leave when you pull them, and it pulls the creature in a straight line closer to yourself. You'd hit him, and he'd move exactly nowhere and then continue his movement as normal. A better example of something that works is Lance of Lethargy.

Lastly, you get Disadvantage for making a ranged attack while an enemy is adjacent to you and, as mentioned before, the enemy is still adjacent to you during the Opportunity Attack.

As far as how gamebreaking it is...it isn't. The only example I could see where this would be relevant is if you were using a reach weapon, and that's a bit of a stretch and not exactly overpowered. You already have a lot working against you, so...go for it!

[Beamer92]

No you made a good point, obviously a melee attack of opportunity happens before he actually moves away so it would kind of make the Grasp worthless. Not to mention the ranged disadvantage which I totally forgot about. I'll just wait until I get a Barlgura to grapple my enemies for me ;)

[Zetakya]

Or hit him with Booming Blade for an instant trigger to the rider :)