Important part in the encryption code:
```p[0] = ((k-10) * ord(s[a])) % 251p[1] = (k * ord(s[a])) % 251p[2] = ((k+10) * ord(s[a])) % 251```
This gives:```p[1] - p[0] = (10 * ord(s[a])) % 251```
Now it's just modular arithmetic:
```ord(s[a]) = (p[1] - p[0]) * inverse(10, 251) % 251```
Full solver code:
```from numpy import arrayfrom PIL import Imagefrom Crypto.Util.number import inverse
img = Image.open('enc.png')image = array(img)x, y, z = image.shapes = [''] * xfor a in range (0, x):    for b in range (0, 1):        p = image[a, b]        tensa = p[1] - p[0] if p[1] > p[0] else 251 - p[0] + p[1]        s[a] = chr(tensa * inverse(10, 251) % 251)print(''.join(s))```
Output:
```Chaos isn't a pit. Chaos is a ladder, Many who try to climb it fail, and never get to try again, the fall breaks them. And some are given a chance to climb, but they refuse. They cling to the realm, or the gods, or love ... illusions. Only the ladder is real, the climb is all there is. RaziCTF{7h3_script_1s_d4rk_4nd_full_0f_m0ds}```