/* https://grabient.com/_gFZgA5gJAgOygCegUsgBhgBmgBhgLHgDLgKw?style=linearGradient&steps=5&angle=315 */

background: linear-gradient(315deg, #1d1a13 0.000%, #421444 25.000%, #660e76 50.000%, #8b07aa 75.000%, #ae01dd 100.000%);

<svg xmlns="http://www.w3.org/2000/svg" width="800" height="400" viewBox="0 0 800 400" preserveAspectRatio="none">
            <!-- https://grabient.com/_gFZgA5gJAgOygCegUsgBhgBmgBhgLHgDLgKw?style=linearGradient&steps=5&angle=315 -->
            <defs>
              <linearGradient id="gradient" x1="0.854" y1="0.854" x2="0.146" y2="0.146">
        <stop offset="0.000" stop-color="#1d1a13" /><stop offset="0.250" stop-color="#421444" /><stop offset="0.500" stop-color="#660e76" /><stop offset="0.750" stop-color="#8b07aa" /><stop offset="1.000" stop-color="#ae01dd" />
              </linearGradient>
            </defs>
            <rect x="0" y="0" width="800" height="400" fill="url(#gradient)" />
          </svg>

["#1d1a13", "#421444", "#660e76", "#8b07aa", "#ae01dd"]

// https://grabient.com/_gFZgA5gJAgOygCegUsgBhgBmgBhgLHgDLgKw?style=linearGradient&steps=5&angle=315
// cosine gradient palette — https://iquilezles.org/articles/palettes/
const float STEPS = 5.0;
const float ANGLE = 315.0;

vec3 palette(float t) {
    vec3 a = vec3(0.345, 0.057, 0.576);
    vec3 b = vec3(0.946, 0.158, 1.324);
    vec3 c = vec3(0.097, 0.102, 0.097);
    vec3 d = vec3(0.711, 0.203, 0.688);
    return a + b * cos(6.283185 * (c * t + d));
}

// N stops sampled from the palette, blended like the CSS gradient
vec3 stops(float t) {
    float n = STEPS - 1.0;
    float x = clamp(t, 0.0, 1.0) * n;
    return mix(palette(floor(x) / n), palette(min(floor(x) + 1.0, n) / n), fract(x));
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 p = fragCoord - 0.5 * iResolution.xy;
    // CSS angle: 0 = up, clockwise; span = CSS gradient-line length
    vec2 dir = vec2(sin(radians(ANGLE)), cos(radians(ANGLE)));
    float len = abs(iResolution.x * dir.x) + abs(iResolution.y * dir.y);
    float t = dot(p, dir) / len + 0.5;
    fragColor = vec4(stops(t), 1.0);
}

[
  [0.345, 0.057, 0.576],
  [0.946, 0.158, 1.324],
  [0.097, 0.102, 0.097],
  [0.711, 0.203, 0.688]
]

Gradient palette editor — #1d1a13 to #ae01dd