Darius Lore: There is no greater symbol of Noxian might than Darius, the nation's most feared and battle-hardened warrior. Orphaned at a young age, Darius had to fight to keep himself and his younger brother alive. By the time he joined the military, he had already developed the strength and discipline of a veteran soldier. The first true test of Darius's resolve occurred in a crucial battle against Demacia, where the Noxian forces were exhausted and outnumbered. Darius's captain called for his troops to retreat, but Darius refused to accept such an act of cowardice. Breaking formation, Darius strode towards the captain and decapitated him with one sweep of his gigantic axe. Both terrified and inspired, the soldiers followed Darius into battle and fought with incredible strength and fervor. After a long and grueling battle, they ultimately emerged victorious.

Seizing momentum from this victory, Darius led his now fiercely loyal troops in a devastating campaign against Demacia. After proving his power on the battlefield, Darius turned his gaze homeward. He saw a Noxus riddled with weakness, where greedy, complacent nobles drained the nation's strength. Seeking to restore his country to greatness, Darius took it upon himself to reshape the Noxian leadership. He identified weak figureheads and violently removed them from their positions of power. Many in Noxus saw Darius's cull as an attempt to seize power, but he had a different plan for the throne. He had been watching the rise of Jericho Swain with keen interest. In Swain, Darius saw a leader with the mind and determination to bring Noxus to glory. Now allied with the Master Tactician, Darius works to unite the nation behind his vision of true Noxian strength.

"A united Noxus could control the world - and would deserve to." - Darius

Pros:
Great ulti
Easy to farm with passive if you are lucky
Has a pull and slow
Can escape with passive happens rarely
Can defend a tower when tower dived
With full stack of the passiv it's alomost a weak ignite

Cons:
Has no escape ability
Mana hungry
Silence can ruin a kill
Very slow without trinity force
Long cooldowns at early levels

I start with the Q

Pros:
Try to get the circle that is painted red for 50% extra damage
Great harassment
When you are in team fights back off a bit and use your Q for the extra damage it will help A LOT

The W
Pros:
It deals a ton of damage with sheen and a crit
It slows and has a longer range then hes normal attack
Try to attack the enemy first and when they are about to escape pull them in with your E and then your W

The E
Pros:
Can do great combo with it
Can pull people in tower range
Passiv armor pentration
Can cancel some ulti with it like Katarinas death lotus
Can save allies
Can steal blue golem with it

You might be wondering why i choose trinity force first it has a movement speed and attack speed where you can stack up your passiv faster.
The crits is just for the W because the W can you crit with and activate sheen at the same time to deal a lot of damage. The ability power is just for the passiv. Warmogs is just for more sustain. Now for the shoes i often go with berserker's greaves when there is a lot of cc then i take mercury's treads or ninja tabi you have to choose on your own thought. Atma's imapler explains it self more crit, armor and damage. Maw of malmortius gives a bit magic resist and damage and the shield can save you many times.
As my last item i usally take Frozen heart for the armor, cooldown reductions and of course the mana

Btw this is NOT a complete guide yet will work on it later if i have time for it so yea good luck with this Darius build. PS my english is not the best so thats my excuse for my bad english