[RPG] Can you really stack all of this on an Opportunity Attack

dnd-5eopportunity-attack

I've stumbled upon a character idea which has quite the potentially to screw someone if they run from you, and I want to know if it is legal in the rules.

A high elf rogue/cleric with the booming blade cantrip and war caster. In theory you get the damage from the weapon, sneak attack (if not used this round), divine strike (if you have it) and booming blade once you hit and the moment he moves…

As example, a rogue 3/cleric 8 character, with rapier would get
7d8 (1 rapier, 2 booming blade, 1 divine strike and 3 once he moves) +
2d6 (sneak attack)
+ dex bonus.

Is everything correct here per the rules?

If so, I think that's pretty insane for something that doesn't really costs any resources.

Best Answer

You usually get everything but Divine Strike (which only works during your turn)

  • The rapier deals 1d8 + Dexterity modifier damage.
  • Booming blade as an 11th level character deals an extra 2d8 if the character doesn't move (3d8 more if they do).
  • Sneak attack adds 2d6 even if you've used in a previous turn this round (see below, emphasis mine, and this related question).

Once per turn [not once per round], you can deal an extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll. The attack must use a finesse or a ranged weapon.

The only thing you may not be able to apply is Divine Strike which says:

Once on each of the cleric’s turns when he or she hits a creature with a weapon attack, the cleric can cause the attack to deal an extra 1d8 ... damage to the target.

As such, you can only apply Divine Strike if the enemy is moving away during your turn.

The enemy has to move away for this to work

In order to deal all of this damage, the enemy does have to move away without using the Disengage action (see below). That is not necessarily an common thing to occur.

If you take the Disengage action, your movement doesn’t provoke opportunity attacks for the rest of the turn.

There is a great synergy, however, with dissonant whispers:

The target must make a Wisdom saving throw. On a failed save, it takes 3d6 psychic damage and must immediately use its reaction, if available, to move as far as its speed allows away from you.

This prompts the opportunity attack against the will of the enemy.

The opponent can stop moving at any time

If the enemy willingly provokes an opportunity attack (i.e. isn't moving because of dissonant whispers), and then you hit with booming blade, they can simply stop moving to prevent the extra 3d8 damage. This would be a very sensible thing for an enemy to do if they've witnessed you use the tactic before or if your table uses the Identifying a Spell rules in Xanathar's Guide to Everything:

To do so, a character can use their reaction to identify a spell as it’s being cast, or they can use an action on their turn to identify a spell by its effect after it is cast.

If the character perceived the casting, the spell’s effect, or both, the character can make an Intelligence (Arcana) check with the reaction or action. The DC equals 15 + the spell’s level. If the spell is cast as a class spell and the character is a member of that class, the check is made with advantage.

Applying Sneak Attack

Don't forget that applying Sneak Attack has it's own requirements:

...if you have advantage on the attack roll. The attack must use a finesse or a ranged weapon.

You don’t need advantage on the attack roll if another enemy of the target is within 5 feet of it, that enemy isn’t incapacitated, and you don’t have disadvantage on the attack roll.

While they aren't the hardest requirements to meet, they do limit the application of the damage to some extent.