What is the highest single round damage a level 20 character can deal?

Question

This is a build optimization question for the maximum damage a level 20 character can do in a single round.

Rules

Restrictions

• No multiclassing, the character must be 20th level of a single class.
• No magic items.
• No party members, you must do this alone.
• No obvious loopholes. (E.g. Polymorph then Power Word Kill or Magic Jar)
• All rules have to be published and no un-official rules are allowed.

The Target

• The monster you are facing has no immunities, vulnerabilities or resistances.

Other rules

• You may have 1 round of preparation then must deal as much damage as possible during the next round.
• You can choose the optimal result for any dice rolls you make (excluding damage rolls)
  • This includes choosing critical hits on attack rolls and assuming that the target fails on all saving throws.
  • It also includes choosing the best result on random tables like the Wild Magic Table for Sorcerers
• For any damage rolls, assume the average result.
• You may choose up to 1 epic boon.
• You also can only cast spells that are from the PH and the XG (this means you are allowed to cast wish, time stop, shapechange or true polymorph)
• You can also use features that maximize damage rolls.
• Also, in this scenario, you would be at the start of the turn order and you can get surprise on the target.
• We can say that when your character started at 1st level its stats were 18, 15, 13, 10, 10, 9
• Lastly, you are only attacking one target.

Given these rules, what is the maximum damage a level 20 character can deal in a single round?

Answer 1

∞

^{well not actually infinite damage, but arbitrarily high damage}

There is no limit to the amount of damage you can deal since we are assuming perfect rolls. The crux of dealing unlimited damage lies in this Wild Magic Surge...

59–60 | You regain your lowest-level expended spell slot.

...and the time stop spell.

The Procedure

• Our character is a level 20 sorcerer of the Wild Magic Sorcerous Origin with the spells time stop and wish.
• They cast time stop and spend four of five turns casting wish to replicate the effect of glyph of warding for an Explosive Glyph near the target (set to trigger on a common command word).
• Each spell cast triggers a Wild Magic Surge for the 59-60 result essentially meaning that the spell slot expended is immediately restored.
• On the fifth turn, they cast time stop again immediately ending the previous time stop (since it affects a creature), and repeat the wish castings in the new set of five turns.
• Whenever the damage is enough for their liking, they let time stop end and say the command word triggering all of the Explosive Glyphs.
• Since the four glyph of warding effects can be of a higher level, each time stop yields 40d8 (~180) or 44d8 (~198) damage (depending on your interpretation of the resulting level of the wish effect).
• Since the last turn in each time stop is spent casting another, our character can essentially take as many turns as they want in one round meaning there is no limit to the amount of damage that can be dealt.

Does the Wild Magic Surge happen before or after the spell slot is expended?

There is one small debatable aspect of this procedure and that is the timing of Wild Magic Surge. If the Wild Magic Surge takes effect before the spell slot is expended, then you could not recover the 9th level spell slot with the spell that expended it.

I personally believe that the timing allows the spell to recover its own slot, because the slot is still expended even if the spell is not completed for some reason (such as counterspell). However, if you interpret the timing otherwise, then our character just needs the Boon of High Magic epic boon to be able to cast the next spell (time stop or wish) and recover the previously used slot.

Answer 2

3752 Damage

The Build

A 20th level Tiefling Wild Magic Sorcerer with

• access to the Wish, Scorching Ray, and Chromatic Orb spells
• the Flames of Phlegethos feat
• the Magic Initiate - Warlock feat (for Eldritch Blast)
• the Boon of High Magic.

Assumptions

Every casting of a spell triggers a Wild Magic Surge with the following effect:

81-82: You can take one additional action immediately.

The Setup Turn

1. The sorcerer converts 7 Sorcery Points into a 5th level spell slot.
2. The sorcerer casts Chromatic Sphere, and expends Tides of Chaos.
3. The DM lets the sorcerer roll on the Wild Magic Table, rolling:

   33–34: Maximize the damage of the next damaging spell you cast within the next minute.

The Damage Turn

1. The sorcerer converts 7 Sorcery Points into a 5th level spell slot

2. The sorcerer casts Wish, duplicating the effects of an 8th level Bestow Curse, choosing to deal an extra 1d8 damage on spells and attacks. This does not require concentration.

3. The DM let the sorcerer roll on the Wild Magic Surge table, using the standard "once per turn" option.

4. The sorcerer casts Wish again, this time duplicating the effects of Hex.

5. The DM lets the sorcerer roll on Wild Magic Surge table, in order to regain a use of the Tides of Chaos ability.

6. The sorcerer uses their remaining spell slots (of 2nd level or higher) to cast Scorching Ray. For each casting, the sorcerer uses the Tides of Chaos ability to gain advantage on one of the attack rolls. Immediately after the casting, the DM lets the sorcerer roll on the Wild Magic Surge table to regain a use of the Tides of Chaos ability.

7. The sorcerer uses their 3 remaining 1st level spell slots to cast Chromatic Orb. The sorcerer follows the procedure in (6) to continue receiving Wild Magic Surges.

8. The sorcerer casts Eldritch blast.

The Math

By using all their spell slots, the Sorcerer shoots a total of 96 standard rays, 9 maximized rays, 3 orbs, and 4 blasts.

Each rays crits, dealing 4d6 (15.66 average) fire damage and 2d8 + 2d6 (16 average) necrotic damage. This totals to 31.66 average damage or 52 maximum damage per ray.

Each orb crits, dealing 6d8 (29.63 average) fire damage and 2d8 + 2d6 (16 average) necrotic damage. This totals to 45.63 average damage per orb.

Each blast crits, dealing 2d10 (11 average) force damage and 2d8 + 2d6 (16 average) necrotic damage. This total to 27 average damage per blast

The total damage is 96 * 31.66 + 9 * 52 + 3 * 45.63 + 4 * 27 = 3752 damage.

Answer 3

Race: Scourge Aasimar +20 and +10 to damage activated as a bonus action.

Lv 20 wizard Evoker,

Feat: elemental adept - fire (goes through damage resistance min damage per dice is 2)

Feat : dragon mark, epic Boon high magic (+one 9th lv spell slot)

Feat: great weapon master +10 dam

Feat: weapon master - greatsword

Prep round:

Action: Cast Delayed blast fireball 12d6 +4d6 for delay(timestop) =64avg

Bonus Action: Activate Radiant Consumption +30dam

Start of Turn

Round 1 Action: cast time stop

(Timestop Round) 0.1 Action: Use Wish to cast glyph of warding to cast lv8 Scorching ray (2d6 x9) set to go off verbally (free action) 144 avg damage

(Timestop Round) 0.2 Action: Cast haste

(Timestop Round) 0.3 Action: apply purple worm poison (12d6dam) to greatsword

(Timestop Round) 0.4 Action: Cast Bestow Curse, Overchannel; as a 5th lv spell; does not require concentration (breaks time stop)

Round 1 Bonus:Cast Dragon breath (fire) on familiar at 5th lv (overchannel) 5d6 save for half = 18 (Lose concentration on DBF and activates it)

Overchannel : damage taken from 2nd use 35(avg)

Round 1 Free action: Set off glyphs of warding verbally. (2d6X2 crit)X9 attacks = 144

Round 1 Haste action: greatsword 2d6X2 crit (14avg) +5st +10 great weapon master ,+42(avg) poison damage =73

Bestow Curse (1d8X2crit) (Overchannel) X 10 attacks =160

Evoker +5

Drongons Breath from familiar 18dam

30+144+73+160+5+18+64=494

494 damage

EDIT: If you are going to down vote please explain why, so i can fix it.