Chronos, despite not meeting the above criterion, is still considered to be an NUA as well, due to the fact that its cost curve is identical to the other NUAs. (NUA cost curve is 2n, with n being equal to the next level.)
There are a total of 15 NUAs: 9 whose effects converge to a certain value, and 6 whose effects are linear.
The converging NUAs never theoretically reach their cap at a finite level. However, because of the fact that the game can only count a certain number of digits, these ancients reach their caps once the effect is within 1/254 (approximately 5.55×10-15%) of the maximum effect.
The 9 converging ancients are listed below, in order of rate of convergence, are listed below:
The non-converging NUAs have no effect cap, but have a linear effect. All six NUAs are listed below. Note that each one of them adds to the duration of a certain skill, by +2 seconds per level..