Quartic Cathedral

The power-four absolute-value map z -> (|Re z| + i|Im z|)^4 + c iterated over the parameter plane at c = -0.378 + 1.015i with half-width 0.140. The steeper fold throws a hooded buttressed massif with fluted ribbing rather than the nautical forms of the quadratic ship. Luminance is an exterior distance estimate from the exact real 2 by 2 Jacobian, the slate atmosphere comes from the smooth escape count, and a minimum-|z| orbit trap grains the interior.