UV dmg increase data collection.
I propose we record some numbers about damage bonuses.
Bonus seems to be 6.5% per Eek5 data below.
Acheron lvl 10:
T2.
Notes:
Damage to blast cubes = damage to jellys = damage to lichens
Damage to ultra blast cubes = damage to darker jellies
-
Nothing:
- Depth 15:
- Depth 16:
- Jelly King:
- Depth 15:
- Depth 16:
- Jelly King:
- Depth 15:
- Depth 16:
- Jelly King: 100 - 130
- Depth 15:
- Depth 16:
- Jelly King: 106 - 137
- Depth 15:
- Depth 16:
- Jelly King: 112 - 156
- Depth 15:
- Depth 16:
- Jelly King: 119 - 157
- Depth 15:
- Depth 16:
- Jelly King:
Small jelly:
Jelly:
T3 Jelly:
Small jelly:
Jelly:
T3 Jelly:
Jelly low:
Small jelly:
Jelly:
T3 Jelly:
Small jelly:
Jelly:
T3 Jelly:
Increase %:
Jelly mid:
Small jelly: 109 - 142
Jelly: 139 - 177
T3 Jelly: 112 - 141
Small jelly: 141 - 183
Jelly: 109 - 146
T3 Jelly: 123 - 157
Increase %:
Jelly high:
Small jelly: 123 - 160
Jelly: 147 - 188
T3 Jelly: 118 - 149
Small jelly: 124 - 164
Jelly: 149 - 193
T3 Jelly: 130 - 166
Increase %:
Jelly very high:
Small jelly: 123 - 160
Jelly: 156 - 198
T3 Jelly: 125 - 157
Small jelly: 124 - 164
Jelly: 157 - 204
T3 Jelly: 137 - 175
Increase %:
Jelly ultra:
Small jelly: 123
Jelly: 165 - 208
T3 Jelly: 131-165
Small jelly: 166 - 215
Jelly: 124 - 164
T3 Jelly: 144 - 184
Increase %:
Jelly maximum:
Small jelly:
Jelly:
T3 Jelly:
Small jelly:
Jelly:
T3 Jelly:
Increase %:
Vanaduke:
Fiend Mid Final Flourish: 217 - 271
Other data is welcome meanwhile for comparison. Also data from people with a lvl 10 acheron with no uvs in jelly runs.
In general, all the monsters at a given depth have the same defense and take the same damage from each hit. Gremlin Menders have low defense (and take more damage), while a few other monsters have high defense (Rock Jellies, Knights).
Yes, I should, but I haven't got there yet, so call it a first approximation.
Still what Khaim said holds true to a certain extent.

In my own experience (tested with swords, one with a damage bonus +med constructs one with +low fiends, on the same level, in the same gear, against the same enemy, compared to a non-UV weapon of the same level and type), low gives a 5% damage increase and medium is 15%. I'll do another run in the coming week and post actual numbers to back this up, but I'm pretty confident in these % increases.
I've not yet been lucky enough to create a high or very high UV, but I'll let you know when I do.
Looking for data from someone with a normal acheron and no bonuses, and a low bonus.
I don't plan on crafting another acheron just to test this.

Nitronome w/ +med and without vs undead:
D26 226/198
D27 229/200
I will be able to eventually test vhigh and max since I rolled an undead medium blast bomb that I'll be turning into a Nitronome. I guess I could test the low/high/ultra too but I'll never craft Bombastic gear (lol) so I'll settle for +2 steps
edit: adding D16 data:
d16 nitronome 95 dmg (no uv), 108 dmg (med uv), 121 (vhigh)
I won't be able to test max for a while but will edit post when I can.
So according to your data:
D26:
Med: 1.141414 ~ 14%
D27:
Med: 1.145 ~ 14.5%
D16:
Med: 1.1368 ~ 13.5 %
VHigh: 1.2736 ~ 27.5%
There are some rounding errors given the nature of integers in computer programming, but I think this confirms about a 7% per level.
I'll run my data after I get some from someone with an acheron with no uvs.
Just thought I would mention some results I picked up just today: a Troika, at completed heat level, deals exactly 100 damage on floor 7 with its charged attack, versus regular opponents. Against an opponent to which it has a medium damage bonus, with the same attack and on the same floor, it did 110 damage.
So in that case medium damage bonus was giving an even 10% boost.

Hey guys, I have expanded upon my data collection for nitronome damage with different magnitudes of damage bonuses. Also, I have observed at multiple depths that the nitronome deals the same normal damage as the leviathan (enough to confidently say that they are equal). Here are my expanded observations:
DEP BSE MED VHI MAX
D16 095 108 121 ---
D19 148 --- 186 ---
D20 159 179 200 220
D21 169 191 213 235
D22 180 203 227 250
D24 193 219 --- 271
D25 195 222 --- 276
D26 198 226 --- 281
D27 200 229 --- 286
D28 203 --- 262 291
@CrashFu
Hm, that seems inconsistent with our data. Were they the same enemy, or where they different enemies? Since there might have different defenses. There could also be rounding errors in the game code, since you were in T1 the damage numbers should be pretty low. So I'll keep observing the other tests for now.
@eek5
Awesome man!
Let's see, % increases:
DEP MEDIU VHIGH MAXIM
D16 1.137 1.274 -----
D19 ----- 1.257 -----
D20 1.126 1.258 1.384
D21 1.130 1.26 1.391
D22 1.128 1.261 1.389
D26 1.141 ----- -----
D27 1.145 ----- -----
AVG 1.135 1.262 1.388
(MEDIUM-1)/2 = 0.0675
(VHIGH-1)/4 = 0.0655
(MAX-1)/6 = 0.065
I think we can conclude from this that the increase is 6.5%. So at max you get a whooping 39% extra damage.
I'll see if I can get some Acheron tests to wrap this up, meanwhile I'll put this number on the wiki.

this is super old thread but i finally collected all the data i could including a new column of low values. I've been stealth updating the old post but thought I'd post a new one for the lows
DEP BSE LOW MED VHI MAX
D19 148 156 167 186 205
D20 159 169 179 200 220
D21 169 180 191 213 235
D22 180 192 203 227 250
D24 193 206 219 245 271
D25 195 209 222 249 276
D26 198 212 226 253 281
D27 200 215 229 257 286
D28 203 218 232 262 291
Yay more tests!
I ran the numbers again. They are pretty much the same as before.
However I noticed something:
Your damage numbers go higher and higher until D23 (about +10 / level), then they start to normalize (+3 / lvl). This is probably due to the nature of 5* weapons and depth scaling.
However, it causes the UV increase to fluctuate between 5% at D19 and 7% at D28.
Maybe we should test this with a 3* item? Supposing the damage of those is constant in all of T3.
All my information was collected at Depth 15 with a plain level 10 Acheron while wearing Fused Demo gear with no UVs.
Depth 15:
Small jelly: 86 - 109
Jelly: 124 - 156
Darker Jelly: 99 - 125
Additionally, Lichens are: 126 - 161

Maybe we should test this with a 3* item? Supposing the damage of those is constant in all of T3.
Current data seems to suggest that the damage of 3* weapons in t3 actually drops of quit rapidly.

Huh, I feel like I can contribute something here, since I was curious myself. My in-depth test of 1 depth with alternating Skolver+Skolver+BarbarounsThornShield combo seemed to approximate results of 7% per level. My weapon uses were Divine Avenger, Gran Faust, and Dread Venom Striker.
Obviously enough, DA and GF basically calculate in the same way in terms of damage it deals to non-weak/non-resistant monsters, yet also align with how much they do when against monsters weak to their element. So even though I say this is against slime, you can also apply this to "against construct" while switching DA and GF's columns around. DVS is just to be looked at separately, but as another set of numbers to run with. With these, the two numbers are (for DA+GF) the first swing then second swing, and (for DVS) the first swing's blade damage then the after-image's damage. They are as follows:
For Depth 9 against slime
. . . . DA . . . .GF. . . Stkr
--------------------------------
Nrm | 108-141 | 128-161 | 50-25
--------------------------------
Med | 123-159 | 143-179 | 57-27
--------------------------------
V H | 138-177 | 158-197 | 64-30
--------------------------------
Max | 153-195 | 173-215 | 71-33
.
From these, it looks as that it's a 7% increase for DA and GF's first swing, but not exactly the same for the second. The DVS's main blade damage seems to match the 7%, though it's after-image attack seems to not follow the same percentage.
Interestingly enough, another thing I saw is that "weaknesses" are additive rather than multiplicative (which I didn't know before), explaining why the difference between the two weapons remain the same through UV-Dmg upgrading (which seems to be a constant 20, though I'm not sure where this number is derived from). Using that logic, some of these numbers may be derived from a "base" damage (that being the first/main strike of the DA/GF/DVS), which could explain why the first swing / blade-damage follows an even 7% increase-per-tier, while the second swing / after-image-damage does not.

New Info based on Tier 2 depths
Fl | [+0 DA] | [+2 DA] | [+4 DA] | [+6 DA] ||| [+0 GF] | [+2 GF] | [+4 GF] | [+6-GF]
-------------------------------------------------------------------------------------
09 | 108-141 | . . . . | . . . . | . . . . ||| 128-161 | . . . . | 138-177 | . . . .
10 | 107-141 | 122-160 | 138-178 | 154-196 ||| 129-163 | 145-182 | 160-200 | 176-218
11 | 110-141 | 126-160 | 143-179 | 160-198 ||| 134-165 | 151-184 | 167-203 | 184-222
12 | . . . . | 126-163 | . . . . | 160-203 ||| . . . . | . . . . | . . . . | . . . .
Bs |---------------------------------------------------------------------------------
14 | 106-146 | 124-168 | 143-189 | 161-211 ||| 137-177 | 155-199 | 173-220 | 192-242
15 | 106-146 | 122-168 | 142-191 | 161-213 ||| 138-179 | 156-202 | 175-224 | 194-246
16 | 110-149 | 127-172 | 149-196 | 169-219 ||| 145-185 | 163-208 | 184-231 | 204-254
.
.
.
Fl | [0 S] | [2 S] | [4 S] | [6 S]
-----------------------------------
09 | 50-25 | . . . | . . . | . . .
10 | 51-25 | 59-28 | 66-30 | 74-33
11 | 50-25 | 58-28 | 66-30 | 74-33
12 | . . . | 57-29 | . . . | 74-34
Bs |-------------------------------
14 | 50-26 | 57-28 | 66-31 | 75-34
15 | 51-28 | 58-30 | 68-33 | 77-36
16 | 51-28 | 58-31 | 67-34 | 77-37
Using my standard "against slimes" since they are abundant, numbers with Divine Avenger and Gran Faust at the top table (DA on left, GF on right to make it easy to compare the elemental weakness bonus that seems more obvious as additive), Dread Venom Striker at the bottom. The numbers 0, 2, 4, and 6 correlate to the Damage Power boosts of None, Medium, High, and Maximum. And again, pair of numbers for DA and GF are the first and second swing, while DVS's pair are the blade-damage then after-image-damage.
So yeah, looks like 7% at first. But diving deeper down, the boost doesn't line up properly by Damage Bonus tier, as comparing Max against Base suggests OVER 50% increase, coming out to a little over 8.5% instead. Another thing to throw into this is that all of my weapons are 5*, which have another layer of calculation on them as they are being weakened by the tier they are in.
So what to make of this info now?

I've looked into the data collected by volebamus.
Doing linear regression on the base damage vs bonus damage we find that; (based on his depth 9 data)
(med damage) = 0.3 + 1.119*(base dmg)
(VH damage) = 1.3 + 1.233*(base dmg)
(max damage) = 2.3 + 1.348*(base dmg)
There seems to be an increasing trend in the intercept value, which is somewhat disturbing. Ignoring that however we can do linear regressing on the bonus level and the linear coefficent, which gives an increase of 5.8% percent per level.
Repeating the same procedure for the depth 16 data we find an increase of 6.6% per bonus level.
This seems to suggest that the bonus percentage does the depth that you are at. This is probably the result of the final damage depending on the base damage in a not trivial way.
Shouldn't you be comparing an Acheron with the UV and one without (rather than one with a UV on different monsters)? I'm assuming here that perhaps different types of monsters have different defences.
Anyway I have some spare flourishes with UVs around so I might test those later (when my internet gets uncapped...).