Unknown #400 (100/1383/0)
1383 refers to the base healing effect. #400 refers to the effect type HealFromMana. By applying the "Aurora Effect", it heals the target for 1383 base for 1383 mana, scaling up to however much is actually healed, given crits and other healing bonuses.
Let's say you have 15k mana, that means that you can potentially heal up to 15k to the entire group given a full mana bar. I believe the 400 in the description, "Channels the power of sunlight, consuming up to 400 mana to heal your group" is an error in the parse, and is calculating the EffectType (Unknown #400) as opposed to the actual value. It should say "Channels the power of sunlight, consuming up to 1383 mana to heal your group".
This spell is quite unique in my opinion, and I'm sure it has it's place.
CORRECTION
After having tested the spell further, I've figured out how it works. Tested on a level 80 Paladin using a level 85 Monk as the test subject.
First of all, this spell will not affect the Paladin casting it in any appreciable amount. Max healing was 12,308 on the Monk.
Since the spell doesn't have a base mana cost, the actual mana cost of the spell is a factor of the total healing amount. If you heal a target for 50% of the total healing amount of 12,308 or 6154, then the mana cost of the spell will be 50% of 1383 or 692. In other words, they scale proportionally.
Also worthy of note is the fact that it cannot crit, or at least I have not been able to get it to crit. I suppose that's fine given the insanely high base healing amount on this spell. It will however crit on the Paladin casting it, for up to 7 on my little Dwarf, which appears to be a factor of the Aurora Effect healing of 1, which usually heals for 2-3 on the Paladin.
Edited, Feb 24th 2018 10:57pm by Shakuden