Hypersensivity: n = the number of non-soul-creatures in play.
Immaterial.
Non-soul-creatures are any creatures other than the four creatures in this thread.
These are mainly immaterial to prevent fractal, TU and mitosis abuse.
Read the yellow parts.
If it doesn't benefit from itself, why is immaterial there to prevent mitosis/fractal abuse?
TU i even understand, since two of them can cause a total of 42 damage unupped, 88 upped. (21 your side of the field, 23 the enemy's)
in other thoughts, Bright Soul is really overpowered, even if it does bring a certain combo with darkness thanks to Nightmare (Nightmaring a low-cost enemy creature) maybe add a -3 to each stat of it? making it require at least 3 non-soul creatures JUST to be played. keep the cpst of it as it is, too.
Bright soul isn't way more overpowered than enlivened soul, since it can have roughly potential doubled stats of enlivened soul and therefore costs nearly double; but since it is more unlikely to happen, that your opponent has a cluttered field, when yourself are not using a trio with darkness (nightmare) or death (aflatoxin), lowering the doubled cost of enlivened soul by 2 in each element seemed appropriate for me.
Now for fractal/mitosis/TU abuse, I have to do some maths:
M = number of enlivened/bright souls on your side of the field
N = number of other creatures, the soul may benefit from, or simply the attack and hp of a single soul
D = potential damage, the souls could cause in one turn, if the rest of the field is cluttered with creatures
So I'm calculating the amount of souls for potential max. damage:
Enlivened soul: I.)23-M=N; II.)D=N*M; I.) in II.) D=-M^2 + 23M
-> if you take the last equation as a function and look for the maxima in it, you see that the highest possible value for D would be 132.25 with an M of 11.5, but since only whole numbers are possible for M, you take 11 or 12, where D would be 132 in both cases. In other words: enlivened souls are the most effective, when you have 11 or 12 of them and 12 or 11 other creatures. This amount of identical creatures cannot be archieved without TUs, mindgate, fractal or mitosis.
Bright soul: I.)46-M=N; II.)D=N*M; I.) in II.) D=-M^2 + 46M
-> same process as above: maximum is for D=529 and M=23; in other words: if your opponent's field is full, you would need 23 bright souls for maximum effectiveness. This amount can't even be archieved by an FG without using the creature-spamming-cards mentioned above.
Edit: Also enlivened and bright soul are immaterial, because otherwise you could copy or spam them without going the intended way by using a abandoned or empty soul.