Why Play Lion?
Lion is good at two things, and both of those things involve making the enemies life a living hell. Simply put, Lion is capable of disabling an enemy for absurd lengths of time and dishing out the damage equivalent of a targeted missile strike on a regular basis.

Lions first and most commonly used spell is his stun Earth Spike, it has good damage and low cooldown. Hex is yet another disable, rendering the enemy target useless for a few seconds on a low cooldown. Mana Drain is, you guessed it, a third disable that slows the target and rapidly depletes them of their mana. His Ultimate is Finger of Death, it is practically a delete button used to finish off your enemies after tormenting them with all of your other spells.

Lion is usually a support, which means his gameplan revolves around protecting his teammates rather than amassing gold. Lion is incredibly independent as a hero, he does not rely on levels gold or items at all to be effective. During the early game, you can continously harass enemies with Earth Spike and keep your mana topped up with Mana Drain. Hex is a little mana heavy, but is useful if you need to keep your enemies locked down for as long as possible. Your ultimate gains more damage if the enemy dies soon after they are hit by it, which means it is generally used as a finisher. The only items you need to worry about getting as Lion is Blink Dagger and Boots of Speeds, a disastrously cheap setup but effective nonetheless.

Lions biggest downside is that he is incredibly vulnerable without help. He has very low health, mobility, and spell range. This means where you decide to place yourself in engagements is very important, as you have to balance between staying safe and laying down your arsenal.