Why isn't Ghirahim playable in Smash 4?

Short answer: Nintendo didn't want to add another magic-wielding swordsman. Robin was put in instead.

Long answer:

Chapter 1

Being disintegrated is not a very pleasant experience. Reassembling something from tiny particles dissipated throughout a vast sky is a task not devoid of skill, especially something so complicated as a living being. And when your mind is a scattered mess along with your exploded body, like the feeling you get when you have a hundred things to do and have already wasted several hours' time, the most excruciating concentration is needed. Needless to say, only the most skilled in magic can actually reconstruct themselves from dust and ashes thrown to the wind.

Former Demon Lord Ghirahim managed to pull it off.

I say "former" as he had previously lost his entire demon army to a boy no older than 17. To regain some self-esteem Ghirahim would probably have liked to continue being known as the Demon Lord, but since there were no longer any demons to lord over, the title didn't hold much merit.

No, today had not been the best day for Ghirahim. Demise, his master, had betrayed Ghirahim and forcefully turned him into a huge, jagged metal blade. To add insult to injury, the boy half Ghirahim's age slew Demise (after a painful battle with the kid's Master Sword) without much trouble. Upon his Demise' death, Ghirahim had promptly dissolved.

Once he had finished reconstructing himself (including his fabulous red cloak), Ghirahim's thoughts finally came together. His vision returned, and he gasped for air. Blue sky stretched out for miles above him. The sound of birds singing and people laughing filled his ears. Ghirahim painfully stood from the sprawled position he had materialized in. He looked about, and found himself on a large sky island, bearing several buildings on its surface and a tent in the center. The edge of the island was only a few feet away, with only sky extending beyond it. Ghirahim started to move toward the drop off, but his head suddenly throbbed so acutely he tripped. With a dull thump, the grey-skinned man fell to the ground once more. "Ow." He said slowly and distastefully as he stared at the pristine clouds. As he stood up, Ghirahim noticed a trickle of blood from where a stone had scraped his arm. "What a pity" He murmured as he realized that his metal demon-skin enchantment was gone. It had essentially rendered him invincible to all but the Master Sword. With the death of his master, Ghirahim realized gravely, much of his own magic had been depleted.

An overwhelming sense of purposelessness came over Ghirahim, and he frowned. Without his master, the nagging sense for bloodshed and sacrifice in his name was gone. Ghirahim now felt like any other being, with no telepathic connections, only himself. It was a unique and freeing feeling, especially for one who had worked to empower another for so many long years, yet it wasn't a very pleasant one. Ghirahim eased his aching body down and sat on the edge of the sky-land, his chin in his hands. He swung his feet back and forth above the void like a child and watched a bird fly in loops off in the distance.

"Are you lost?"

Ghirahim whirled around, and beheld a young girl, perhaps seven or eight years of age, looking at him with a concerned expression. She had an odd ponytail that stuck straight upwards from her head. His face hardened.

"No. Are you?"

The girl wore a thick maroon coat. She ignored the comment. "My name is Kukiel." She smiled and extended her hand. "What's yours?"

Ghirahim didn't take it. "kooky-what?"

Kukiel looked Ghirahim over. "You look like a clay statue. You OK? Why don't you come to my house for some tea?" She immediately started skipping down the road, away from the ledge. After a few leaps she stopped, and turned around. "Coming?"

Ghirahim stared at the girl for a moment, then gingerly got to his feet and dusted himself off. He was about to politely refuse, but the thought of the Kukiel's parents horrified faces at the sight of his grey skin and white hair made him inwardly chuckle. He reconsidered, and smiled as warmly as he could. "I accept the offer of tea at your house. Lead the way."

The girl scampered off and Ghirahim followed, striding gracefully.

The inside of the house was quaint, with a stone floor at the front of the room and raised wooden section at the rear. A dome shaped fireplace was situated at the back wall, with windows and a cabinet on the right. A table and two chairs sat in the center of the home and a bed was tucked in the corner. Kukiel immediately started darting around the house, gathering things for tea.

As soon as he had taken in his surroundings, Ghirahim snapped his fingers, making his cloak disappear in a flash of rhombuses. He sat himself down on one of the chairs and crossed his legs, while inspecting some tiny diamond shape lights floating around his fingers. It reminded him of insects buzzing around a light source. "Residual magic." He mumbled. "I'll have to work on that."

"What did you say?" Kukiel poked her head out from behind the kitchen door.

"Nothing of your concern."

Kukiel frowned. "Where did your coat go?"

"I said, nothing of your concern."

"Okay okay!" She shrugged and disappeared back into the kitchen.

The girl reappeared carrying two mugs of red-gold liquid. She set one on front of Ghirahim, and he scowled at the beverage. She plopped herself down in the other chair and started swinging her legs. Her ponytail swung back and forth, like the tail of a puppy when it is in a good mood. Kukiel picked up her mug and started slurping loudly.

While still leaning back in his chair, Ghirahim stuck his long tongue out and into his mug of tea, tasting the beverage. He concealed a smile as Kukiel looked up disgustedly.

"That's weird."

"Oh? How so?" Ghirahim said after he had reeled his tongue in.

"Your tongue is too long! See?" Kukiel stuck out her own tongue but it didn't reach far enough for her to taste her tea.

"Really..? Maybe your tongue is too short and I should be the one who thinks it is weird"

Kukiel cocked her head and furrowed her eyebrows. "I hadn't thought of it that way. Which of our tongues is normal?" She tried in vain to look at her tongue.

Ghirahim chuckled. "Where are your parents?"

Kukiel stopped trying to lick her nose, frowned, and sighed. "I dunno. They are always so busy, what with Smash auditions and all that. I'm sure they're somewhere on the island."

"Smash?"

"Yeah. All sorts of crazy people from all over have been visiting Skyloft. Knights, swordsmen, monsters, and Hylians alike. The audition booth is in the Bazaar. Isn't that why you're here? To join Smash, I mean? You look like the type of person who would. Sorry, I mean, you're certainly not from around here."

Ghirahim sat forward, interested. "I had no prior knowledge of this 'Smash'. What is it?"

Kukiel brightened up. "They say only the best and strongest warriors get in. It's some kind of club. I've only seen one guy get admitted, but everyone expected that. Everyone else who's tried has either been turned down or offered 'trophy status', which doesn't sound very nice. They wouldn't even let me audition because I was too young."

"You auditioned?" Ghirahim smirked.

Kukiel squirmed. "Well I tried too. Mom and Dad don't know." She looked down, and added in a quiet whisper, "pleasedonttellthem!"

Ghirahim smirked. "I'm not evil in that way."

"What?"

Ghirahim leaned back. "Just who is this great warrior they let in?"

Kukiel beamed. "Link!"

Ghirahim shot to his feet and glared at the girl, knocking over her now-empty teacup and the chair he had been sitting in. Low and menacingly, he whispered, "What did you say?"

Kukiel shrank back. "L-Link. He saved Skyloft, but I still don't really understand how… Are you OK?"

Ghirahim clenched his fists. "I thought I was done with him. I thought I could escape to the past and finish my task. But No. The little wretch destroyed me. He ripped the purpose and determination out of me when he slew Demise." Ghirahim knew Kukiel had no idea what he was talking about, but he decided to leave Demise's betrayal out of his little rant. "I have nothing. I don't know what to do." Ghirahim paused for a moment and put a hand to his forehead. Then a grin spread across his face, like a gash tearing in brittle fabric.

"Could you please tell me your name?" Kukiel, still quite perturbed by the mysterious white-haired man's mood swings, timidly asked.

Ghirahim jerked himself out of his reverie and looked at the girl curiously, only now realizing that she still didn't know his name. "Lord Ghirahim. Ruler—Ahem—former ruler of all the surface below." Ghirahim bowed in the girl's direction. Kukiel looked back at Ghirahim questioningly. He sighed "Link's fault", picked up his chair and promptly sat down, blowing snowy hair out of his face.

Kukiel shifted uncomfortably. "Ghirahim… I have one more question."

Ghirahim rested his chin on his hand. "What."

"Um… are you a boy or a girl?"

Ghirahim's eyes bugged and he almost lost his balance. He knew his face looked somewhat effeminate, he had heard that plenty of times, but he had hoped at least his tight clothing would be evident towards his masculinity. Ghirahim's title, "Lord Ghirahim", should have also evidenced this fact, but Kukiel didn't seem to notice.

"I am..." Ghirahim sputtered, "Of the male gender."

"Okay thanks." Kukiel smiled. "Mister Ghirahim, can we please go see if they will accept you into Smash?"

Ghirahim's wry smile returned. "Please. Lead the way."

Kukiel giggled and bolted for the door. As soon as she was out of sight, Ghirahim stood. He raised his hand to a few inches from his face, and snapped his fingers again. The pointy diamond-patterned cloak reappeared on his shoulders, this time with no small rhombuses lingering around his fingers. Pleased, Ghirahim made for the door, but stopped a few feet in front of it. He wanted to try one more thing. Slowly, Ghirahim raised his arm high into the air and pulled back, the hilt of a black sabre materializing. Ghirahim soon held a full sized blade, summoned from thin air. "Good." He said. "Link will remember this."

An excited, childlike voice could be heard outside the door, but it wasn't Kukiel. "Oh wow wow wow! Really!? Where is he?"

Ghirahim had just enough time to dematerialize his sword before the door was thrown open. A short boy, probably younger than Kukiel, burst through. He froze and stared at Ghirahim in awe, but wasn't silent for long. "Wow! You're him right? Mister Guillotine? Were you really once king of the surface? Did you actually fight Link? How did he win?"

The boy had hair that resembled the work of a poorly-skilled botanist.

Ghirahim scowled. "Out of my way" He snarled through clenched teeth. He pushed past the boy and through the door. Outside stood Kukiel with her head down.

"That's Gully" She said apologetically. "He's… enthusiastic. I didn't think he would be so rude. Sorry."

There was a banging on the door into Kukiel's house. Ghirahim inwardly smiled. He had locked it behind him telepathically. Kukiel moved towards the door to let the child out. "Just ignore him OK? It'll be fine when we get to the Bazaar. He'll leave us alone once he sees…" Kukiel turned around to see Ghirahim already striding toward the red tent in the center of the island. She sighed and unlocked the door. "C'mon Gully! And don't be such an idiot next time!"

Gully ignored the comment. "Who is he? And why is he wearing a pillowcase?

"Shut up. I think he's sensitive. Like Fledge at the academy."

Gully didn't respond and instead sprinted off after the tall former-Demon Lord. Kukiel sighed again, then saw Ghirahim disappear into one of the Bazaar's many entrances.

"He's gonna get into Smash. I know it."