What is the point of the throwing mechanic in Delayed Blast Fireball?

Question

Delayed Blast Fireball has a unique clause about physically grabbing and throwing the spell itself:

If the glowing bead is touched before the interval has expired, the creature touching it must make a Dexterity saving throw. On a failed save, the spell ends immediately, causing the bead to erupt in flame. On a successful save, the creature can throw the bead up to 40 feet. When it strikes a creature or a solid object, the spell ends, and the bead explodes.

Casually, I've always assumed that this clause exists to act as some sort of counterplay to the mage casting Delayed Blast Fireball - the mage starts growing this ball of flame next to the party, the dextrous rogue decides to wing it and grab the bead, heroically beating the Dex Save and immolating the mage with his own spell.

Except this scenario would never realistically happen - a caster can end his concentration at any time possible, so as soon as he sees the rogue beat the Dex Save, he can just release concentration.

So why does Delayed Blast Fireball have this specific property?

I cant see this being utilized offensively by the mage himself, since wizards usually have pretty low Dex, and it would be pretty anticlimactic/humiliating to blow yourself after charging up this bomb.

Answer 1

D&D 5e is built as a team game - consider the spell a team asset

Let's look at how your team can exploit this feature of the spell.

Situation 1: does the enemy know that there is a wizard in your group?

If not, then with the wizard hiding around a corner (or if the wizard is a halfling and hiding behind a Medium or large sized ally/PC) then the ability to cast this spell but have someone else throw it (the party Rogue or Monk for a high dexterity save) is a way to surprise your enemy with a fireball that they didn't see coming.

Situation 2: I want to keep the wizard out of harm's way

Party is in a room, but the wizard is in the adjacent room due to having low HP; one spell or missile hit and she may bite the bullet. Wizard casts delayed blast fireball, Rogue (or Monk) runs in, grabs it, and with a bonus action dashes out and then hurls it at the enemies ...

These are sample ways to exploit the portable nature of this spell. Your own group will doubtless come up with other team tactics that could take advantage of it.

Is it risky?

Yes. Stack the odds in your favor, as a team, by boosting the Rogue's dexterity saves. If the Rogue is an Arcane Trickster, they might be able to cast haste on themselves and get advantage on the save.
If the rogue is multi-classed as a barbarian, advantage on dexterity saving throws against spells comes at 2nd level of Barbarian.

The price of failure? A grand and glorious, and even cinematic disaster. This might be one of those "as a last resort" tactics if the party is in a serious bind.

Another use for that feature ...

Cast that and flee, leaving it in the middle of the cavern passageway, or hallway, as the pursuit rounds the corner. If they touch it or run into it or try and pick it up, kaboom is the likely outcome.

Answer 2

Presumably that's what the Dex save is for.

You can see the rogue going after the fireball and try to react by detonating it. If you time it right, you'll blow them up. If they're quicker than you, you'll fail.

This is also why letting a spellcaster drop concentration in the middle of someone else's action is a bad idea.

There is a moment in time when the rogue grabs the fireball to throw it away.

If the wizard is behind the rogue on initiative, then on the wizard player's turn, he can decide what he's doing at that moment, but it can't be "blow up the fireball" because we've already established that the rogue threw the fireball away. That's how initiative works.

If the wizard is ahead of the rogue on initiative, then on the wizard player's turn, he can decide he's blowing up the fireball, or not, or that he's going to watch the fireball carefully and blow up anyone who touches it. That last option is called "readying an action". If he didn't ready an action, then his attention is elsewhere at that moment (because he's doing some other action).