Lina

Lina the Slayer is a ranged Intelligence hero, adept at destroying enemy heroes fast and delivering massive bursts of magical damage, making her one of the most effective gankers in the game. She possesses immense damaging capabilities all throughout the game, but is very fragile. Two of her fiery spells are her main source of damage, Dragon Slave sends a wave of fire to burn enemies in her path while Light Strike Array stuns them with a concentrated pillar of solar flame. Each of her spells deals great damage early on and has a low cooldown. Her Fiery Soul bolsters her attack and movement speed exponentially every time she casts a spell, which gives her scaling damage for the later game. Laguna Blade, her ultimate, is her ace in the hole. Lina fires off a huge bolt of lightning at a single target, dealing colossal damage. Laguna Blade's damage is staggering in early-mid game, and late game is still enough to destroy frail enemy heroes. Dragon Slave, Light Strike Array, and Laguna Blade are incredible flaming nukes that can incinerate her target instantly, and Fiery Soul allows her to transition into a strong and fast physical attacker. Though her power falls from its peak late game, mana-boosting and damage-increasing items can be purchased to keep herself up, serving as the team's magical semi-carry, dishing out intense burning damage with her attacks and spells.

Tips

 * Combining Light Strike Array with a guaranteed stun such as Vengeful Spirit's Magic Missile or Sven's Storm Hammer makes Lina a serious ganking force early on.
 * Positional items such as Eul's Scepter of Divinity, Blink Dagger, Force Staff or Phase Boots can help you a lot landing Light Strike Array and thus your whole spell combo without relying on other heroes.
 * Always cancel the backswing animation after casting your spells, as Lina suffers from long animation times.
 * In teamfights it can be very beneficial to quickly focus on low-HP or support heroes, as Lina has very good nuking abilities.
 * Laguna Blade should not be used always as a finishing blow, since that can waste most of the spell's massive damage. It is best used to cripple enemy carries or obliterate their supports; but using it when its damage far exceeds the target's remaining HP is a waste. There is a temptation to use it on fleeing heroes as it is the only one of Lina's abilities that is long range and target-unit; but it is wiser to build Blink Dagger instead to avoid having to expend it.
 * When paired with Pugna or Shadow Demon, both of whom have percentage-based damage-increasing mechanics; Lina's burst damage becomes gigantic (a sceptred level 3 Laguna Blade will do about two thousand damage alone) to the extent where she can assassinate enemy heroes with a significant gear/level advantage over her.
 * If Lina has the basic items she needs; it is wises to augment her physical attack for the sake of Fiery Soul. Almost uniquely among Int supports, Lina's rightclick becomes a serious threat if she attains a level advantage (owing to her enormous Int growth and her passive ability). Some basic items for this build are Daedalus, Eye of Skadi and Monkey King Bar, as well as some form of lifesteal.
 * Lina's Laguna Blade can hit for around 2500 damage (without factoring in magic resistance) if she combines Aghanim's Scepter and Refresher Orb, granting her enormous nuking power.
 * While unmentioned purchasing an Ethereal Blade if the farm is available combined with an Aghanim's Scepter and Lina's naturally high Intelligence gain will give you a perfect combination of survivability through stats, armor and Ghost form and an enormous increase (roughly 2534 not counting the damage from Ether Blast) in damage output allowing Lina to instantly kill most low to average HP heroes provided that she lands all of her skills during the Ether Blast. The slow provided by Ether Blast also comes in very handy in landing Light Strike Array. This build would make Lina somewhat similar to Morphling's Shotgun build.
 * If Lina is tending to be targeted first (this is a very common tendency), some survival-increasing / utility items will be of great use.
 * Some players advocate building a Dagon in place of an Aghanim's Scepter, as it is cheaper and ultimately does more damage (through both its active and its bonus to her attack damage). Unlike Aghs, however, it does nothing to make her more durable.
 * For Fiery Soul to take to its peak, cast Dragon Slave, Light Strike Array, and Laguna Blade successively to take the speed-enhancing effect of Fiery Soul to its maximum potential.

Trivia

 * The original Lina Inverse "The Slayer" was modeled after the main character from the novels/anime/manga Slayers where Light Strike Array, Dragon Slave and Laguna Blade are all spells used by the original Lina Inverse.
 * Lina was the first hero to be made in Dota 2.
 * Lina's line "Better to burn out than fade away" is a reference to the Neil Young song, "My, My, Hey, Hey".
 * The line also appears in the suicide note of Kurt Cobain.
 * In Warcraft DotA, Lina and Rylai the Crystal Maiden were not depicted siblings at all, as evident by their different surnames (Inverse and Crestfall, respectively) and their bios having no mention of each other. In Dota 2, their bios have been significantly altered, depicting them as rival siblings, even having special responses when attacking, meeting, and killing each other.