HonkaiImpact 3rd: How damage multipliers work

By base damage, I mean damage, inflicted by a Valkyrie using her skills, which have their own factors. You can calculate the base damage of the Valkyrie using the following formula:
ATK × skill, which deals% ATK Physical / Elemental DMG = base damage

Void Drifter will act as an assistant.
ATK value Void Drifter is 1094. Her combo attack, Void Flechette, with some help from a passive skill deals 320% ATK Physical Damage.
In this way: 1094 × 3.2 = 3500, i.e Void Drifter without stigma and weapon bonuses will inflict 3500 units of damage to the target. This is her base damage.

Now let's prepare Void Drifter to the real battle:
● Schrodinger (T): +205% Total DMG;
● Dark Jixuanyuan (M) and (B): +40% Physical DMG;
● Tranquil Arias: +50% Total DMG, +15% Physical DMG;
● she has passive bonuses: +50% Total DMG и +15% Crit DMG;
● she is a MECH type and will attack an enemy of type BIO: +30% DMG.

Formula for multiplying physical damage (built-in bonuses, stigmata, weapon, superiority / weakness by type):
(1 + Total DMG) × (1 + Physical DMG) × (basic 200% Crit DMG + additional Crit DMG) × (1 + superiority / weakness by type or ± 0.3)
↓
(1 + 2.05 + 0.5 + 0.5) × (1 + 0.4 + 0.15) × (2 + 0.15) × (1 + 0.3) = 17.54

We find out, how much damage will it do Void Drifter fully equipped:
base damage × final multiplier
↓
3500 × 17.54 = 61390

It's important to know: elemental damage (Elemental DMG) is an every element (ice, electricity and fire), so that you you can use elemental ... ah ... whatever with the Valkyrie any element (physical damage - obviously, not an element).

Here I will be supported Hawk of the Fog.
My Hawk of the Fog It has 1372 ATK, and her combo attack, Kei: Taranic Heels, with a little help from a passive skill, inflicts 430% ATK Lightning Damage.
Her base damage will be ...
1372 × 4.3 = 5899

And now Hawk of the Fog crumples:
● Monet (T): +15 Total DMG, +30% Lightning DMG;
● Ishikawa Goemon (M): +20% Total DMG, +25% Lightning DMG;
● Ishikawa Goemon (B): +35% Lightning DMG;
● two stigmata Ishikawa Goemon: +30% Total DMG;
● Nuada’s Revenge: +40% Lightning DMG;
● passive bonuses: +30% Lightning and additional +45% Lightning DMG;
● she is a PSY type and will attack a MECH type enemy: +30% DMG.

Elemental Damage Multiplication Formula (built-in bonuses, stigmata, weapon, superiority / weakness by type):
(1 + Total DMG) × (1 + Elemental DMG) × (1 + superiority / weakness by type or ± 0.3)
↓
(1 + 0.15 + 0.2 + 0.3) × (1 + 0.3 + 0.25 + 0.35 + 0.4 + 0.3 + 0.45) × (1 + 0.3) = 6.54

We find out, how much damage will it do Hawk of the Fog fully equipped:
base damage × final damage multiplier
↓
5899 × 6.54 = 38579

(1 + received physical / elemental damage) × (1 + received Total DMG) - a simple formula for stigma, weapons and skills, which force the enemy receive more damage, such as the: Isaac Newton (B), May: Beach Party (M), Blood Dance.
note: received damage from source (eg, skill Scarlet Chain Valkyries Swallowtail Phantasm) works the same, like all of the above, but only for source / owner.
Generally, received damage is a very strong multiplier.

Final Damage Multiplication Formula:
base damage × final physical / elemental multiplier × received damage × received source damage × level itself damage multiplier (if there)

Following the formula, with "superimposed" on the enemy Newton (B) and May: Beach Party (M) + level effect (enemies get on 50% more physical damage) final damage Void Drifter will be like this:
3500 × 17.54 × (1 + 0.31 + 0.15) × (1 + 0.5) = 134444

Final Damage Hawk of the Fog with "superimposed" on the enemy Newton (B) and May: Beach Party (M) + level effect (enemies get on 50% more elemental damage):
5899 × 6.54 × (1 + 0.31 + 0.15) × (1 + 0.5) = 84489

Planck (M) provides 51% physical damage.
Marco Polo (M) provides 50% crit damage.

Planck (M)
50% Total DMG × (50% Physical DMG + 51% Physical DMG) × basic 200% Crit DMG
Basic 1000 ATK × [final multiplier]
↓
(1 + 0.5) × (1 + 0.5 + 0.51) × 2 = 6.03
1000 × 6.03 = 6030

Marco Polo (M)
50% Total DMG × 50% Physical DMG × (basic 200% Crit DMG + 50% Crit DMG)
Basic 1000 ATK × [final multiplier]
↓
(1 + 0.5) × (1 + 0.5) × (2 + 0.5) = 5.625
1000 × 5.625 = 5625

6030 > 5625
Planck (M) > Marco Polo (M)

Monet (T) provides 15% all damage, 30% lightning damage and 117 ATK.
Shakespeare (M) provides 51% lightning damage and 91 ATK.

Monet (T)
(50% Total DMG + 15% Total DMG) × (50% Lightning DMG + 30% Lightning DMG)
(basic 1000 ATK + 117 ATK) × [final multiplier]
↓
(1 + 0.5 + 0.15) × (1 + 0.5 + 0.3) = 2.97
1117 × 2.97 = 3317

Shakespeare (T)
50% Total DMG × (50% Lightning DMG + 51% Lightning DMG)
(basic 1000 ATK + 91 ATK) × [final multiplier]
↓
(1 + 0.5) × (1 + 0.5 + 0.51) = 3.015
1091 × 3.015 = 3289

3317 > 3289
Monet (T) > Shakespeare (T)

Thales (M) provides 20% all damage and causes the enemy to receive 20% more fire damage.
Shakespeare (M) provides 51% fire damage.

Thales (M)
(50% Total DMG + 20% Total DMG) × 50% Fire DMG × 20% Received Fire DMG
Basic 1000 ATK × [final multiplier]
↓
(1 + 0.5 + 0.2) × (1 + 0.5) × (1 + 0.2) = 3.06
1000 × 3.06 = 3060

Shakespeare (M)
50% Total DMG × (50% Fire DMG + 51% Fire DMG)
Basic 1000 ATK × [final multiplier]
↓
(1 + 0.5) × (1 + 0.5 + 0.51) = 3.015
1000 × 3.015 = 3015

3060 > 3015
Thales (M) > Shakespeare (M)

Thales (M) provides 20% all damage and causes the enemy to receive 20% more fire damage.
Leeuwenhoek (M) provides 20% all damage and 20% fire damage.

Thales (M)
(50% Total DMG + 20% Total DMG) × 50% Fire DMG × 20% Received Fire DMG
Basic 1000 ATK × [final multiplier]
↓
(1 + 0.5 + 0.2) × (1 + 0.5) × (1 + 0.2) = 3.06
1000 × 3.06 = 3060

Leeuwenhoek (M)
(50% Total DMG + 20% Total DMG) × (50% Fire DMG + 20% Fire DMG)
Basic 1000 ATK × [final multiplier]
↓
(1 + 0.5 + 0.2) × (1 + 0.5 + 0.2) = 2.89
1000 × 2.89 = 2890

3060 > 2890
Thales (M) > Leeuwenhoek (M)

Different enemies can have different defenses.
Impair reduces the physical defense of the enemy and is very important for physical attackers.
Physical shield and physical resistance reduce the damage taken by the enemy or even neutralize it.
Elemental Breach reduces the enemy's elemental defense and is very important for elemental attackers.
Elemental Damage Resistance reduces or eliminates elemental damage taken by the enemy.