Shadow Dash will trigger Ki Barrier when he finishes his dash, meaning a short range dash will trigger the shield sooner.
Stand United will trigger Ki Barrier when he arrives at his destination. A shield won't be granted if the ability is cancelled.
Twilight Assault is an offensive ability that doesn't deal damage itself, but grants Shen bonus magic damage on his next 3 basic attacks within 8 seconds. If the ability hits an enemy champion, the ability grants even more bonus magic damage and also grants 50% bonus attack speed. Enemies hit are also slowed when moving away from Shen.
Versus minions and monsters, this ability grants a flat bonus on top of the bonus magic damage that the ability already grants, capped up to a certain amount.
This makes last-hitting very easy for Shen: activate this ability, and have between 30 – 175 free bonus magic damage for your next 3 basic attacks.
This ability has a low cooldown and a relatively low energy cost: if you have at least one point in Shadow Dash, each enhanced basic attack restores between 30 / 35 / 40 energy.
If you have enough energy to cast Twilight Assault and need to restore energy, cast it and hit any enemies you find.
Spirit's Refuge is a defensive ability that creates a protective zone around the Spirit Blade for 1.75 seconds, granting 100% dodge chance to all allies in the zone.
This ability is very effective against enemy champions that rely on basic attacks, such as Twitch, Vayne, or Olaf.
This ability may be hard to master in the beginning, but the only thing you have to do to make it useful is to cast Twilight Assault just before Spirit's Refuge. By doing this you'll bring your Spirit Blade to you and activate the protective zone around you.
When clearing the jungle or fighting enemies who only fight with basic attacks, it is helpful to activate the ability when Ki Barrier is not on to ensure that neither ability's damage mitigation is wasted.
Shadow Dash is an offensive ability that makes Shen dash in the target direction dealing physical damage that scales with bonus health to all enemy champions hit and taunting them for 1.5 seconds. Passively, this ability allow Twilight Assault's and Shadow Dash's damage to restore 30 / 35 / 40 energy.
This ability is a great engage tool if you manage to aim at the right direction and at the right moment.
If you manage to taunt an enemy champion, you will be hit by his basic attack for 1.5 seconds. To avoid the potential damage, you can cast Spirit's Refuge on yourself to have the 100% dodge chance, if the Spirit Blade is not already on yourself, you must cast Twilight Assault just before.
A great combo is: Q > W > E. This will grant you bonus magic damage on your next 3 basic attacks, a 100% dodge chance for 1.75 seconds, and a taunted enemy at your mercy.
A more offensive combo would be to Shadow Dash through your opponent to make sure that your Spirit Blade passes through your enemy to trigger the amplified bonus damage.
Stand United is a global range defensive ability that shields the target allied champion for 5 seconds; after a 3-second channel, Shen and his Spirit Blade blink to the ally's location.
This ability is what makes Shen a great splitpusher despite lacking any innate turret taking or waveclear abilities, as he can easily join his team if they get engaged on or force a 5v4 in his team's favour if the enemy team tries to deal with him.
The base values of this ability are really high. A well casted ultimate on an allied champion requiring help can dramatically change a team fight.
This ability has one of the highest AP ratio in the game with (+ 130% AP). This makes AP Shen a game changing champion: Stand United on near-death carries can grant them an unexpected shield that can be potentially higher than their entire health bar.
Shen is mostly played as a tank or an attack speed / attack damage bruiser. His kit has bonus health scaling for Ki Barrier's shield and Shadow Dash's damage, a dodging zone with Spirit's Refuge, and a global range ultimate that allow him to blink to an allied champion while giving them a powerful shield. Due to his ultimate, Shen is also a good splitpusher as he can easily join his team if a teamfight breaks out.
Titanic Hydra and Sterak's Gage are great for a bruiser Shen. The former grants Shen much needed waveclear while significantly boosting his damage due to the item's health scaling. The latter provides yet another shield for Shen which combined with Ki Barrier, make him even tankier.
Sunfire Cape grants him health, armor and some magic damage while at melee range. The passive is also excellent to solve Shen's innate lack of waveclear.
An item classified as an offensive item is Guinsoo's Rageblade. It offers ability power, attack damage, and attack speed, all going well with Shen's kit.
Another great item for Shen is Wit's End. It provides Attack Speed, Magic Resist, bonus on hit magic damage and MR shred and steal. This help Shen deal more damage without sacrificing too much tankiness.
Shen can also be played as an ability power bruiser.
Another unsual choice would be Nashor's Tooth, granting attack speed, ability power, cooldown reduction and on-hit magic damage.
Landing Shadow Dash is crucial for Shen as he has no ranged abilities. Dodging the ability will leave him extremely vulnerable to kiting, render his Twilight Assault useless and cripple his energy pool.