The purpose of this build is to add an alternative to a raw tank Malphite, and it winds up creating an unstoppable force that can shatter enemy teams with a brutal AoE disable, shutting down DPS and carries, slowing enemies, and assisting allies all while doing some serious damage.

9x Greater Mark of Magic Penetration
Some people might not be aware that all of Malphites damage is magical, and magic penetration will naturally boost your overall damage output, which is essential for this build.

9x Greater Seal of Health
These runes will help you make up for your lack of early game beefiness, and help to keep you in lane much longer.

9x Greater Glyph of Scaling Cooldown Reduction
This will help cut down on cooldowns later in the game, ensuring you have your ult for teamfights.

3x Greater Quintessence of Health
Same as Seals.

I chose a 9/0/21 build to take the decreased cooldowns and magic penetration, while bolstering my summoner spells ( Ghost and Teleport) and increasing my regeneration. The increased experience gain and enhanced buff duration will also help out quite a bit as long as you stay in your lane while being able to manage acquiring blue buff.

NOTE: Do NOT take Blue Buff if someone on your team who it would help more is available to take it (e.g. : Ezreal Malzahar Veigar)

Starting:
Doran's Shield
Helps you stay in lane much longer at the beginning

Early game:
Boots Ruby Crystal Amplifying Tome
Pick up a pair of boots, a crystal, and a tome to start building your midgame items.

Mid-Game:
Sorcerer's Shoes [Haunting Guise]] Sunfire Aegis
The Sorc Shoes, Guise, and Sunfire Cape will massively increase your overall damage output, while providing you with the health you need to be a successful tank. With these items, you are a massive threat and can destroy enemy teams with ease.

Late Game:
Randuin's Omen Banshee's Veil Frozen Heart
The Omen will provide an AoE slow which should hit their entire team if you can land your ult and use it immediately after. The veil will boost your magic defense and health, and make sure you aren't disabled in teamfights to use your ult. A frozen heart is a great item to have if the game drags on.

Maxing Seismic Shard is a must as its your main source of damage, and provides and awesome Move Speed buff and Slow.

Ground Slam is your bread and butter AoE ability and used in combination with your ult, can devastate enemy teams.

Brutal Strikes isn't all that useful, so I choose to max it last.

Unstoppable Force does is exactly what it says. Using this skill turns you into a battering ram with one goal in mind: tearing apart the enemy team. Try to hit as many people with it as you can, and aim for the squishier champs.

Ghost Is an awesome skill to take, because it can be used in combination with Seismic Shard to massively increase your movespeed and help you maneuver around in fights.

Teleport is an all around useful skill to take as it can help you defend turrets, pick up large farms, and get closer to the fight. Always look for an opportunity to teleport to an allied lane and help them out.

Flash can also be useful to surprise enemies.

Overall, this build can be truly incredible if used correctly.
Best of luck on the battlefield.

-Hashani