Lion is a ranged intelligence hero that is usually played as a support hero. He is item independent, has good nuke damage, and is arguably the best disabler in the game, but this all comes at the cost of being very squishy and having poor move speed.
Skills
Skill and max Earth Spike first, your damage dealing stun.
Skill Hex at level 4 but max it second.
Skill Mana Drain at level 2 but max it last. Use it to steal mana from enemies during the laning phase, making Earth Spike spammable.
Always get your ultimate, Finger of Death, at levels 6, 11 and 16. Use it to burst down enemy heroes but try to avoid kill-stealing.
Items
Starting Items: Courier or Observer Wards, a Set of Tangos, a Healing Salve, Gauntlets of Strength, and an Iron Branch.
Early Core: Flying Courier, Observer Wards, Boots of Speed, Magic Wand, Bracer.
Mid Core Options: Observer Wards, Tranquil Boots or Phase Boots, Mekanism or Force Staff or Drums of Endurance.
Luxury Extensions: Blink Dagger, Scythe of Vyse, Vladmir’s Offering, Heaven’s Halberd, Eul’s Scepter of Divinity, Ghost Scepter, Black King Bar, Necronomicon, Aghanim’s Scepter.
Situational Items: Smoke of Deceit, Dust of Appearance, Sentry Wards, Gem of True Sight.