Here are some pen name suggestions based on your provided keywords, categorized for easier selection:

Emphasizing Darkness & Sadness:

• Obsidian Tears
• Shadow Quill
• Raven's Lament
• Midnight Bloom
• Dusk Weaver
• Weeping Willow
• Black Swan Song
• Mournful Dove
• Gloomhaven
• Ink-Stained Sorrow

Emphasizing Romance & Fantasy:

• Gemstone Heart
• Wind Whisperer
• Crystal Tears
• Sapphire Moon
• Emerald Dawn
• Ruby Dusk
• Golden Feather
• Silverwing
• Azure Dream
• Celestial Kiss

Emphasizing Apocalypse & Death:

• Death's Quill
• Apocalypse Rose
• Ruin's Embrace
• Shadowfall
• Ember's Kiss
• Obsidian Dawn
• Grim Fable
• Last Breath
• Withering Bloom
• Fallen Star

Combining Elements:

• Darkwind's Embrace (combines dark, wind, romance/fantasy)
• Weeping Gem (combines crying, gemstones, sadness)
• Happy Apocalypse (ironic juxtaposition of happiness and apocalypse)
• Duckling's Lament (unexpected, whimsical, yet sad)
• Crystalline Ruin (combines gemstones, apocalypse, sadness)

More Abstract Options:

• Aether
• Nyx
• Seraphina
• Morwen
• Zephyr

Remember to check if the name is already in use before settling on one. Consider also the overall tone and style of your writing when making your final decision. The best pen name will depend on your personal preference and the specific project.