The combination of olive‑tinged cap, heavy slime, and large, ornamented spores makes C. majestatica one of the most morphologically distinctive New Zealand Phlegmacium species.

Cap: 30-70 mm diam.; at first hemispherical with a strongly incurved margin, later umbonate‑convex, rarely expanded; fleshy. Colour dark date‑brown, always with a distinct olive‑greenish tinge. Hygrophanous. Surface covered with a very thick slime layer (up to 3 mm); near the margin grooved or wrinkled. No squamulose veil remnants present. Margin striate in over‑mature specimens.
Lamellae: Emarginate, crowded. Colour argillaceous to coffee‑brown or ochraceous‑brown. Edges whitish, fimbriate.
Stipe: 40-80 x 8-15 mm, cylindrical, robust, becoming fistulose at maturity. Colour brown or lighter than the pileus. Surface dry, apically glabrous to longitudinally fibrillose; below the annulus with squarrose squamules. Ring very conspicuous, pendent, strongly striate, immobile; whitish or concolorous with the stipe; margin often with brown gelatinous patches derived from the pileus margin.
Context: Brown throughout.
Odour/taste: Not distinctive.