This is after my research, i compiled all the information in my head about RO damage reduction

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For falcon assault, Sacrifice and acid demonstration

Element enchanted - Flame laucher, enchant poison, dark water and etc

Remove the immune muffler 20% neutral damage reduction

*Take note weapon element - VVS fire damascus WILL still be reduced by immune muffler

example

4k falcon assault with fire damascus:

against GR + immune = 800 damage

4k falcon assault with flame laucher:

against GR + immune = 1000 damage

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For Sonic Blow

same theory as enchantment stated above
weapon element - fire katar WILL NOT be affected by immune muffler

Example:

Katar 140 attack 10k sb:

against immune = 8k damage

Fire katar 140 attack 10k sb:

against immune = 10k damage

Katar 140 attack 10k sb WITH enchant poison:

against immune = 10k damage

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Race Element Size:

RO calculate damage by this 3 category basically (excluding turtle general etc) I think i saw somebody posted a guide on card modifier damage

so same for reduction…

Equipment:

Tyrfing shield 25% reduction size
Poop hat 10% reduction by race
immune muffler 20% reduction by element

base damage dealt = 10k

Damage taken = 10,000 x 0.75 x 0.9 x 0.8
= 5,400 damage

Another example to show contrast:

Equipment:

Thara frog shield 30% reduction race
poop hat 10% reduction race
immune muffler 20% reduction element

base damage dealt = 10k

Damage taken = 10,000 x 0.6 (sum up the same category) x 0.8
= 4,800 damage taken

Hope this is understandable

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WOE damage reduction:

Melee normal hits = 0% reduction
Melee skills (those affected by safetywall except falcon assault) = 40% reduction
Ranged skills (affected by pneuma) = 40% reduction
magic spells (SG JT MS) = 50% reduction

correct me if im wrong