Dark Willow

Consider using Shadow Realm to secure range creep last hits.

You can dodge ranged attacks and many spell projectiles with Shadow Realm.

If in trouble, you can potentially do Shadow Realm into teleport out play.

Dark Willow is great at picking off isolated heroes with no escape or dispel due to insane Bedlam damage.

In teamfights, focus on getting off Terrorize, Bramble Maze and Cursed Crown timely and then burst an isolated target with Bedlam.

If the game opens up for you, you can transition into right-clicker with Aghanim's Scepter and attack speed talent.

You can use your Bedlam on initiators on your team and do all your damage while staying back in fights.

Dark Willow is squishy at the start and doesn't trade well.

Under effect of Cursed Crown make sure not to get too close to your allies or they will be stunned too.

Bedlam does a lot of damage to a single target. Share the damage with allied units.

Items that provide dispels are generally good against Cursed Crown, Bramble Maze and Terrorize.

Black King Bar is great against Dark Willow's disables and magical damage output.

Don't clump up in teamfights for Terrorize and Cursed Crown.