How does the Flames of Phlegethos racial feat interact with the sorcerer’s Metamagic option Empowered Spell?

If I have both the Flames of Phlegethos feat and the sorcerer’s Metamagic option Empowered Spell, can I re-roll the same die twice?

The description of the second benefit of the Flames of Phlegethos tiefling racial feat says (XGtE, p. 74):

When you roll fire damage for a spell you cast, you can reroll any roll of 1 on the fire damage dice, but you must use the new roll, even if it is another 1.

The description of the sorcerer’s Metamagic option Empowered Spell reads (PHB, p. 102):

When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.

You can use Empowered Spell even if you have already used a different Metamagic option during the casting of the spell.

Can you re-roll the same die with both features, or only once? That is, if you re-roll a die with one of these abilities, does the other ability let you re-roll it?

The "You must use the new roll" makes it sound like you cannot, but in general abilities can can override how other abilities work. Is the "keeping the new roll" restriction limited to re-rolls from that ability, or does it apply to all re-rolls from any source?

There is another interpretation of "You must use the new roll." There is a feat called Savage Attacker which reads:

Once per turn when you roll damage for a melee weapon attack, you can reroll the weapon’s damage dice and use either total.

If you compare this to the language in the previous two abilities, you see that the "re-roll and must use the new roll" could be viewed as the alternate to "re-roll and use either roll", and therefore imposes no restriction on other features re-rolling the die.

Does Empowered Spell metamagic work over multiple turns?

The Sorcerer’s Empowered Spell metamagic option reads

Empowered Spell When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.

While the spell Immolation reads (emphasis added):

Flames wreathe one creature you can see within range. The target must make a Dexterity saving throw. It takes 8d6 fire damage on a failed save, or half as much damage on a successful one. On a failed save, the target also burns for the spell’s duration. The burning target sheds bright light in a 30-foot radius and dim light for an additional 30 feet. At the end of each of its turns, the target repeats the saving throw. It takes 4d6 fire damage on a failed save, and the spell ends on a successful one. These magical flames can’t be extinguished by nonmagical means.

If a sorcerer with +5 CHA uses Empowered Spell on Immolation to re-roll 3 of the 8d6 and the target fails its save on its next turn can the Sorcerer re-roll an additional 2 dice of the 4d6 damage?

This question might include whether Empowered spell should be read as:

"When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice [from that damage roll] up to your Charisma modifier"
or
"When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice [for that spell] up to your Charisma modifier"

Are dice re-rolled together or sequentially for Chaos Bolt with Empowered Metamagic?

The Sorcerer’s Empowered Spell metamagic option reads

Empowered Spell When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.

While the spell Chaos Bolt reads:

You hurl an undulating, warbling mass of chaotic energy at one creature in range. Make a ranged spell attack against the target. On a hit, the target takes 2d8 + 1d6 damage… If you roll the same number on both d8s, the chaotic energy leaps from the target to a different creature of your choice within 30 feet of it. Make a new attack roll against the new target, and make a new damage roll, which could cause the chaotic energy to leap again.

If Sorcerer chooses to Empower Chaos Bolt and has a Charisma modifier of at least +2 do they need to re-roll all of the dice that they wish to re-roll at once or can they re-roll one d8 then, if it does not match, re-roll the other?

As an example:

The sorcerer casts Chaos Bolt and rolls a 7 and an 8. They use Empowered spell and re-roll the 7 getting a 3. Can the sorcerer re-roll the 8?

Can I use Empowered Spell on spells cast with a Wand of Magic Missile? [duplicate]

The Sorcerer’s metamagic features has the following general rules:

At 3rd level, you gain the ability to twist your spells to suit your needs…You can use only one Metamagic option on a spell when you cast it, unless otherwise noted.

The Empowered Spell metamagic states:

When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.

The Wand of Magic Missiles states:

While holding it, you can use an action to expend 1 or more of its charges to cast the magic missile spell from it.

My question is does the process of activating the Wand equate to the sorcerer casting the Magic Missile spell and thus it becomes a suitable target spell for enhancement using the Empower Spell metamagic? Or does the casting occur from the wand and not from the sorcerer, thereby rendering the spell invalid for metamagic enhancement?

What is the interaction between Empowered Spell and Booming Blade or Green-Flame Blade?

Can you reroll the damage dice that come as part of the melee weapon attack? That is, is the melee weapon attack part of the damage for the spell?

Empowered Spell reads:

When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.

Booming Blade and Green-Flame Blade read:

As part of the action used to cast this spell, you must make a melee attack with a weapon against one creature within the spell’s range, otherwise the spell fails.

Is there a way to get the effects of the evocation wizard’s Empowered Evocation on a magic missile at a much lower character level?

At level 2 a Lore Master wizard has the Spell Secrets ability. This allows the wizard to change the damage type of a spell, like magic missile, from force damage to fire damage.

If a character multiclasses into Phoenix Sorcerer she can use her Mantle of Flame ability to add her charisma bonus to one fire damage die roll.

Or a character could multiclass into Dragon Sorcerer and use the Elemental Affinity ability at level 6 to get the same effect on a variety of damage types.

Frozen, flaming or electric magic missiles sound kind of cool. Adding bonus damage sounds powerful.

Do these builds work? Is getting a level 10 ability this early too unbalanced?

Interaction between potent cantrip and empowered spell: Thunderclap

According to DnD 5e wizard evoker subclass lvl 2 feature Sculpt Spell, you could prevent 1 friendly adjacent creature from taking damage from a Thunderclap cast by your evoker (it would automatically save the CON save and suffer no damage).

Also, according to evoker lvl 6 feature Potent Cantrip, cantrips that would normally do no damage on a failed save now do half damage (including, I’m assuming, thunderclap). Taken to the letter, this would mean that getting the lvl 6 feature Potent Cantrip would be detrimental to your character, at least with regard to the casting of Thunderclap, since the spell would now harm your friend near you? Am I getting this right?

It may well be the case, but it seems a little bit unfair. Could you choose to apply the Potent Cantrip feature only to your enemies when casting a Thunderclap? Could you choose not to apply Potent Cantrip to a given Thunderclap cantrip casting at all to prevent friendly fire?

How to calculate the expected damage increase from Empowered Spell?

In D&D 5th Edition the Sorcerer Metamagic ability Empowered Spell states the following:

“When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.”

How do you calculate the increase in the average damage when you use this ability? It seems to me you would use this to only reroll dice that came up 3 or less however you have less of a chance of increasing your damage when you reroll a 3 than when you reroll a 1.

I know something of probability from playing tabletops for so long but figuring this out is beyond me.

Empowered Spell before and after Spell Bombardment

Suppose we have an 18th-level wild magic sorcerer, and suppose that he has a Charisma modifier of at least +2. He casts Fire Bolt, hits, and rolls a 1 on the d8 for damage. Expending a single sorcery point, he empowers the spell and rerolls the die. This time, it’s an 8. Our sorcerer now uses Spell Bombardment to get an extra d8 of damage. This one is a 1 as well. Does the Empower Spell from before allow him to reroll this second die as well?

When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.
You can use Empowered Spell even if you have already used a different Metamagic option during the casting of the spell.

Beginning at 18th level, the harmful energy of your spells intensifies. When you roll damage for a spell and roll the highest number possible on any of the dice, choose one of those dice , roll it again and add that roll to the damage. You can use the feature only once per turn.