Undying

Undying the Almighty Dirge, is a melee strength Hero who serves as a formidable tank; his abilities forcing opponents to either kill him first or suffer powerful debuffs in a teamfight. Decay is a spammable skill that reduces the enemies' Strength, making them more fragile as the fight goes on. Soul Rip can act as both a powerful heal or nuke. This is empowered by Tombstone, which acts as a tank in itself by summoning Zombies to slow Undying's foes while it is alive. Finally, Flesh Golem increases all allied damage by a significant percentage, and helps keep Dirge alive as his team kills the enemy.

Zombies
Zombies cannot be controlled. Zombies will not spawn to attack buildings. Zombies will not spawn in fog of war.

Tips

 * One of the best skills to use early game is Decay: it's quite spammable, and will make ganking easier. You can easily get first blood if you're laning with a good partner.
 * Decay is very useful even if left at level 1. Max it when team battles begin to start: you can spam it even more and make enemies squishier.
 * Undying can be played in many ways: if you're going for a more supportive role, use your Tombstone and your Flesh Golem to slow the enemies while spamming Decay, then let your lane partner get the kill. Otherwise, use Soul Rip to finish a Hero while there are many creeps nearby: this way it will deal more damage.
 * Don't use Soul Rip to harass, but use it to heal a friendly hero or to finish off enemies. This is more effective if there are many units nearby, such as creeps if you're laning, or heroes if you're initiating.
 * While initiating, use Tombstone and Flesh Golem, then Decay/Soul Rip: this way these skills will deal more damage.
 * Though his spells are individually quite cheap, you will almost always have mana problems since both Soul Rip and especially Decay are very spammable. Consider getting Arcane Boots during the laning phase, then disassembling it once you have enough to buy the remaining pieces of a Bloodstone. You can then convert your standard boots to Phase Boots allowing you the mobility and chase power to keep Flesh Golem's powerful aura on the right targets during a teamfight.
 * If you don't have enough money to buy a Bloodstone in time or you'd prefer cheaper items, try to make you as tanky as possible: if you're initiating, enemies will target you first. That's why you need an early Vanguard and/or a Hood of Defiance if the opposing team has a lot of nukers. Other useful items that increase your HP are Rod of Atos, which will probably solve most of your mana problems too, and Heart of Tarrasque.

Trivia

 * Undying was originally an intelligence hero, having the Heartstopper Aura as part of his original skill set. His skill set was completely changed upon becoming a Strength Hero, thus giving the aura to Necrolyte.
 * Undying makes several references to the Left 4 Dead series, saying names of special infected, campaign names, and even the title itself in his dialogue.
 * One notable reference is Undying's line "No dead are safe from Blueheart Bob," which is similar to the famous Left 4 Dead "Chicago Ted" graffiti line ("No zombie is safe from Chicago Ted").
 * Undying also references the Half Life series in a rival line towards Tinker. Dr. Kleiner, who shares his voice actor with Tinker, has a pet headcrab named Lamarr. Headcrabs are small, parasitic creatures, who attach themselves to the head of their victims, after which the victims turn into zombies.
 * Undying's Invoker response is a reference to the 6.72's leaked changelog, where Invoker's name "Kael" was mistakenly translated into "Carl".
 * A dirge is a somber song of mourning or grieving, typically performed at a funeral.