Izanami, bringer of death (S8 Unranked)

Izanami's passive makes her a ver niche ADC in that she does more, the more health she has missing. This makes items like the Asi good for her since the increased life-steal on reaching 35% health lets her stay in a situation most ADC might want to avoid to get the kill.
Pen items can be a waste of gold on her as she also gains penetration from her passive.
Qin's Sai are really the power behind her auto though in my opinion. The additional health damage, again combined with her natural pen makes her a tank killer.

Abilities
1. Gives greater attack speed and power.
2. Slows enemies and does a decent bit of damage to boot
3. Escape or gap close, makes her versatile and hard to kill. (Can be canceled with CC)
4. Silences in an AOE and does decent damage.
Passive: The closer she is to death, the more damage she does, up to 20% for each 10% of her missing health. Her basic attacks increase in projectile speed with higher attack speed and only trigger items on first target hit per attack. (Though life-steal seems to prock through all hit targets from my observation).



Main build:
Cowl
Gives some early sustain as well as base life-steal you'll use throughout the game. Good starter item with perks for duo laning in Conquest, or team fighting in Assault, Joust, etc.

Asi + boots
Attack speed is not only great for ADC in general, it also makes her attacks move faster in the air. Attack speed boots are my first go-to for early game attack speed, followed by Asi for the health sustain.
Since her passive allows her to do more damage and pen at lower health, Asi also allows you to stay that extra few minutes since it gives an additional 35% life-steal at low health. As Izanami, your goal is to kill it fast, so be careful how long you stay, the buff only lasts so long.

DeathBringer
A lot of builds I've seen like to use Rage for a crit item, I disagree with this choice. Death bringer is able to do 30% additional damage with a 25% crit chance, as fast as you attack with Izanami, you'll be critting fine and HARD with Deathbringer as your item.

Qin's Sai
In my opinion, this is your bread and butter. No matter what you're hitting, you're doing 3% health, faster and harder. Health tanks start to look like tasty targets instead of frustrating walls of damage mitigation, just watch out for CC. On squishier targets, this combined with the crit from Deathbringer really just demo's anything that can't either out damage you or stun you.

Executioner
Great for power and that last bit of attack speed, plus it helps to remove any physical resistances from the enemy bruisers or tanks again making you an enemy shredder.

Shadow Shuriken
Gives attack speed and power while disabling healing effects or life-steal by 40%. Not a bad choice against another ADC that only wins out because their life-steal + Power is to much for you. Works well with an auto champion since it will simply re-apply as fast as you hit them instead of them getting away and healing outright.

Purification beads
MUST HAVE for Izanami. Her biggest downfall is CC. Her escape does not make her immune and you can be stunned while in the middle of it. If a heavy CC comp starts to dump on you, pop beads AND THEN 3 out or you might just be screwed.

While I have Hunters Cowl mentioned, either cowl should be used depending on the situation and how you feel about it. One works better with a good team around you, the other would help in a disadvantaged situation.

LATE LATE game if you're rolling in gold and have the ability, ditch your boots for a swiftness potion, grab a power potion, and see what other items might fit your personal taste for the character. Adding in whatever is missing from one of the two builds I've listed doesn't work badly either.

IMPORTANT TIPS:
Izanami's 1, while active, prevents her from attacking through multiple targets. It is best NOT to use this until you're clear to hit the enemy god only. Using this in a bunch of minions will mitigate your healing and probably prevent you from securing the kill if that ONE wisecrack minion decides to face tank for their team.

Izanami's 2 slows but also does a lot of damage. Use it to engage or disengage as you see fit. Can also be used to slow enemies before retreating, or helping a low teammate get out alive.

Izanami's 3, while making her relatively invisible, does not make her invulnerable, keep this in mind.

Izanami's 4 has a slight delay but silences everything in a team fight. This works really well to help you fight off ability-based enemies and can be used to start, end, or disrupt a fight as needed.

Good luck and happy hunting.