Dota 2/Abaddon the Lord of Avernus

Abaddon is a melee strength hero who can be played as a support or a semi-carry. His ability makes him a naturally durable hero. His spammable Mist Coil lets him repeatedly deal damage to his enemies or heal his teammates, provided that Abaddon has the health to support it. His Aphotic Shield is a useful protective spell that purges and absorbs damage, while being able to hurt enemies if it absorbs too much or lasts long enough. Abaddon's passive, Curse of Avernus places a debuff on enemies he attacks, buffing allies who do the same. Finally, Abaddon's ultimate, Borrowed Time, briefly turns all damage dealt at him into health, greatly increasing his tankiness.

Mist Coil
Mist Coil makes Abaddon hurl a projectile toward the targeted hero, dealing damage if it's an enemy while healing if it's an ally, at the cost of some of his health. With a 5 second cooldown, it is very spammable, and can often keep teammates alive much longer or do a huge amount of damage in teamfights, provided that Abaddon has the health pool to support it. Abaddon is able to suicide with the health drain of Mist Coil, and with the spell's low cooldown it isn't hard to do so.
 * Ability: Target Unit
 * Affects: Heroes
 * Damage Type: Magical
 * Self-Damage: 50 / 75 / 100 / 125
 * Damage/Heal: 100 / 150 / 200 / 250
 * Mana Cost: 75
 * Cooldown: 5

Aphotic Shield
Aphotic Shield places a shield on the targeted ally, absorbing a set amount of damage. Once the shield reaches the damage limit or the end of its duration, it will explode, dealing damage equal to the maximum damage it can absorb to enemies around the shielded target. It has a low cooldown, especially on higher levels, so Abaddon can place an Aphotic Shield on multiple allies at once. A great feature with Aphotic Shield is that it removes disables and debuffs from the target upon casting, which can potentially save an ally from being focused down instantly.
 * Ability: Target Unit
 * Affects: Allied Heroes
 * Duration: 15
 * Max Damage Absorbed: 110 / 140 / 170 / 200
 * Burst Radius: 675
 * Mana Cost: 100 / 105 / 110 / 115
 * Cooldown: 12 / 10 / 8 / 6

Curse of Avernus
Curse of Avernus makes Abaddon's attacks place a slowing debuff on any enemy unit he attacks, causing any ally to attack the slowed unit to gain increased movement speed and attack speed. It is a great ability to secure kills on priority targets, and Abaddon's natural tankiness lets him get the debuff on enemies despite his melee range.
 * Ability: Passive
 * Debuff Duration: 2.5
 * Buff Duration: 4.5
 * Slow: 5 / 10 / 15 / 20
 * Movement Speed Bonus: 15%
 * Attack Speed Bonus: 10 / 20 / 30 / 40

Borrowed Time
Borrowed Time removes all debuffs on Abaddon when cast and briefly turns all incoming damage in health, causing attacks to heal Abaddon. The ability will automatically activate when Abaddon's health drops below a certain threshold. This ability gives Abaddon much of his innate survivability, being able to survive extreme burst damage. This lets him stay in the middle of teamfights longer than other supports, and can sometimes play the role of a tank by making enemies waste high-damage spells on him at the start of a teamfight.
 * Ability: No Target
 * HP Threshold: 400
 * Duration: 3 / 4 / 5
 * Mana Cost: 0
 * Cooldown: 60 / 50 / 40
 * Scepter Duration: 5 / 6 / 7

Aghanim's Scepter can be bought by Abaddon and will increase the duration of Borrowed Time.