Abaddon
- You can deny yourself using
Mist Coil. - The self-damage on Mist Coil can be absorbed by
Aphotic Shield and can heal you during 
Borrowed Time. - Mist Coil can heal and damage siege creeps.
- You can put Aphotic Shield on siege creeps.
- Aphotic Shield will always detonate for the full damage regardless of damage absorbed. This means that you can replace a shield on an ally to detonate it on demand for the damage.
Abaddon's cast animations are long and the cast range on Aphotic Shield is garbage. If you're pushing/defending with your team and you're worried about enemy initiation, try casting and canceling Aphotic Shield on your team's highest priority hero. Not only will this constantly keep you in range to cast the shield, but if you've got beastly reactions you can almost instantly wipe off any disable.- If you get attacked by a hero while you have Aphotic Shield on, the game still acts like you've taken damage from that hero. This means that
Healing Salve, 
Clarities, 
Bottle, 
Urn of Shadows, 
Blink Dagger, 
Recall, and sleeps all get canceled. - You don't need to actually complete an attack to get the
Curse of Avernus buff. During chases or escapes, you can animation cancel an attack on a neutral or a creep to give yourself a free 15% move speed bonus without having to wait through Abaddon's full attack animation. If you have Tranquils this is doubly important since it allows you to get the move speed buff without breaking your boots. - Curse of Avernus works on towers. Why doesn't Caustic Finale work on towers? That'd be sweet.
- Aphotic Shield doesn't absorb any damage during Borrowed Time, all of it goes to healing.
- There are very few situations in which you want to manually activate Borrowed Time pre-Agh, but it can be useful if you need to disjoint a projectile like a stun.
- The self-damage taken from
Armlet of Mordiggian can heal you under Borrowed Time. This is a bug. - Abaddon's a great aura slut since most teams rarely want to waste the time necessary to kill him in a fight.
Versus
- The burst damage radius on Aphotic Shield is pretty huge (675).
- If you have a nuke that does >400 damage, you can instakill Abaddon without Borrowed Time ever triggering.
- If you don't trust your team,
Eul's Scepter's is a great Abaddon counter since it can waste 2.5s of Borrowed Time. 
Ancient Apparition 
Ice Blast prevents Abaddon from healing during Borrowed Time.
Bristleback
- If you're against heroes with global skills (Ancient Apparition,
Invoker, 
Zeus), be sure to face in the inside of your Fountain when healing to take advantage of 
Bristleback. - Bristleback damage reduction does not work on towers.
- Spam spells to keep
Warpath stacks up when roaming around the map if you have the mana regen to support it. - Spam
Quill Spray in the fountain before TPing out to charge up Warpath stacks. - A highly effective hero to take advantage of stacked ancients with. By the time you get a
Vanguard you should be able to take a three stack of ancients literally without even looking. - Bristle is tied for the fastest turn rate in the game. If you're laning against a ranged hero with a slow projectile, you should absolutely take advantage of this by gracefully pirouetting before every right click harass attempt.
Versus
- Bristleback damage reduction is calculated based on his orientation to the hero who owns the source of damage he's taking. Summons deal damage based on their own position, not the hero who summoned them.
Magic Wand is core against this guy ALL GAME LONG. Unlike other heroes who stop spamming once the laning phase ends like 
Batrider or Zeus, 
Bristleback needs to mash his spells for the whole game. No matter what role you're playing, you should always get a wand or a stick.- Quill Spray is physical damage, so if you get a
Ghost Scepter this guy can't do anything except wipe his nose on you. - Quill Spray is not reduced by damage block, so building a
Crimson Guard against Bristleback won't help you as much as you'd hope. - You can purge Goo stacks (
Manta Style, Eul's Scepter's, 
Diffusal Blade). - Bristle is all about whittling down your armor and barraging you with physical damage. Stacking armor helps mitigate his damage output (
Shiva's Guard, 
Assault Cuirass, even a 
Ring of Basilius is good). - Hexes disable the Quill Spray passive from Bristleback, but they do not disable the damage reduction passive. The only way to completely shut off this skill is with
Aghanim's Scepter 
Doom. 
Razor makes Bristleback's life incredibly hard. Bristle can't go on Razor thanks to 
Unstable Current slowing him every time he casts Goo and Bristle has no easy way to stop Razor from slurping up his damage with 
Static Link.
By tsunamis at Reddit