Does a Scourge Aasimar take half damage from its own Radiant Consumption effect?

In Volo's Guide to Monsters, the Aasimar playable race has the following trait (pg. 105):

Celestial Resistance. You have resistance to necrotic damage and radiant damage.

So they take only half damage from radiant damage.

The Scourge Aasimar sub-race also have this ability (pg. 105):

Radiant Consumption. Starting at 3rd level, you can use your action to unleash the divine energy within yourself, causing a searing light to radiate from you, pour out of your eyes and mouth, and threaten to char you.

... at the end of each of your turns, you ... take radiant damage equal to half your level (rounded up). In addition, once on each of your turns, you can deal extra radiant damage to one target when you deal damage to it with an attack or a spell. The extra radiant damage equals your level.

So let's say a level 10 Scourge Aasimar activates this ability. During their turn, they make a nearby creature take 10 radiant damage. Does the Aasimar themselves take 5 also, or do they only take half of that because of their Celestial Resistance?

In other words, does their Celestial Resistance negate (some of) their own self-dealing damage from Radiant Consumption?

• Is the "in addition" part relevant to your question, since you ostensibly wouldn't be targeting yourself with that extra radiant damage equal to your level? Only the part where you and those within 10 feet of you take radiant damage equal to half your level would be potentially affected by your own resistance.
– V2Blast
Jul 29, 2018 at 21:15

The level 10 Aasimar would take 2 radiant damage

you ... take radiant damage equal to half your level (rounded up)

Resistance affects any source of damage unless specified otherwise:

If a creature or an object has resistance to a damage type, damage of that type is halved against it

Then you round down from$\frac{5}{2}$ to get 2:

There’s one more general rule you need to know at the outset. Whenever you divide a number in the game, round down if you end up with a fraction, even if the fraction is one-half or greater.

General Formula (thanks to Medix2 in comment)

To calculate this for any given level (L) you can use this formula: $\left \lfloor { \frac {L + 1}{4}}\right \rfloor$

Adding 1 to the level accounts for the rounding up of the half-level damage. This is because, when working with fractions, X + 1 rounded down is identical to X rounded up. Since all factors are now rounded down we can just multiply across. Half of $\frac {L + 1}{2}$ gives us our formula.

Yes a Scourge Aasimar resists their own Radiant Consumption, at first I thought the reason they stated taking half level radiant damage rounded up was to simplify the calculation for resistance, but then I realized two things. One anything you halve is always rounded down unless otherwise specified, Two resistance always applies unless it specifies that the damage cannot be reduced in any way like some abilities

For example Oath of Redemption Paladin 10th level ability Aura of ?(I can't remember what it's called) paraphrased of course, When a creature within the aura takes damage you can choose to magically take the damage instead, damage taken in this way cannot be reduced in any way, and any additional effects do not transfer

However since it doesn't state the damage can't be resisted, by process of elimination that means it can be resisted and the damage halved as a result

Basically the only time damage isn't reduced by having resistance is if it specifically says it can't be resisted, or in the case that the creature has an ability which bypasses resistance(See Elemental Adept)