This is a small guide for new Lillith players who have no idea how to use her properly.

I'm not gonna talk about DPS Lillith, only healer. So, if you want to play Lillith as a healer you have to pick the CURSED ACCORD talent (Decrease the Blood cost of your abilities by 35% and increase your Healing done by 15%, but reduce the damage you do by 25%) you will surely do less damage, but more heals/less Blood cost.

Her skills/abilities:

HEART OF CRIMSON

Shoot a bolt of blood from your Heart-Cube, dealing 625 damage per shot. Consume no ammo while Hex or Swarm affect a Champion. You use your Blood pool to keep yourself alive.

BLOOD HEX

Lillith hexes an enemy or ally, dealing current Health damage to enemies or Healing allies for an increasing value based on duration. You regenerate Blood while this ability is active. 4s CD

SWARM

Lillith summons a circular swarm of bats to Heal her allies and damage her enemies. This ability can be channeled to increase its effectiveness after activation. Lasts 5.75s and costs 825 Blood to cast. 3s CD

DEATH WINGS

Lillith leaps into the air and gains air control. Reactivating this ability slams directly down, dealing damage in a small area. Costs 350 Blood to cast. 2s CD

BLOOD MOON (ultimate)

Lillith grants her team pure Lifesteal — unaffected by Anti-heal — for 8s while gaining increased Movement Speed, jump height, and Blood regeneration.

First of all, you need to know that Lillith is affected by the cauterize effect (unless she ults) so it's better for you to find a safe spot to heal your allies without getting hit. When it comes to the item part, I'd recommend Chronos to be able to spam your heals as much as you can and then buy Haven which will reduce the damage you take, the damage reduction works on her blood HP so it makes her like a semi-tank-sup. Her ultimate is also very strong so you can buy Moral Boost as your third item if you want or if you don't have to get any other specific item to counter some comps (like crowd controls etc) or Master Riding on certain maps. But prioritize Chronos in every case. Kill to heal is also a good choice because it's unaffected by cauterize and it will allow you to get more of your blood back when you or your ally get a kill or elimination. You can take Nimble if you want more movement speed, it's always nice to be able to move faster so you can reach your teammates faster whenever they play aggressive (and if you combine Nimble+Resilience it will help you to get out faster of Evie's Ice Storm her ultimate, and also works with Grohk's ultimate, Inara's cripple etc). And last, you can pick Veteran to make her more tanky than she already is, but you don't really need it if you already have Haven lvl 3.

Her main loadout is pretty simple, you put a mark (Blood Hex) on one of your allies and you will regenerate your blood as long as it's active on someone, works both on ally and enemy. But, don't forget about the cauterize effect! After you put your mark on someone, you can now use your second ability and put a lot of Swarms to heal others, like your tank point, your damage and your off tank. And what's even better about Swarm is that it will deal a lot of damage to enemies as long as they touch it or stay in it, so you could zone someone with it or finish someone off or just put it on point to damage the enemy tank point and it will regenerate your blood as long as it deals damage to the enemy. I personally put my mark on the flanker first, sometimes I will switch to my off tank, point tank or damage. Although, it's better to give your mark to anyone who plays aggressive, but, in some cases, you can give it to your point tank or your damage, it will depend on the situation and on your teammates' playstyle. Ex: if they keep running away from you, just give them a mark so they get heals a little bit then switch it to someone else who needs it. If you want to spam your Blood Hex you have to use your third ability Death Wings which will reduce the CD of Blood Hex by 1s (thanks to the Sanguine Pact card) and add to it Chronos and you will be able to spam it frequently. Note that Lillith will automatically start regenerating her blood when she drops below 50% blood HP and it will regenerate on it's own up to 50% of her blood health, not more.

How should I use her skills?

Put Blood Hex on one of your ally, then you can use Death Wings then reactivate Death Wings to fall down and you will get your Blood Hex back in a very short amount of time (but you need to have the Sanguine Pact card in your deck otherwise it won't work) and then you can put your Swarms and then repeat the same procedure. If you get flanked a lot you could bait them to attack you and then use your ult before they burst you down and then go join your teammates. This way, the enemy flanker will lose a lot of time.