Tarr the Terrible

I'm quite fond of this strategy as it's not very RNG dependant at all. In fact I haven't lost once using this strategy. The pet swap is timed so that the XP-gaining pet takes no damage. The strategy is as follows:

Tarr the Terrible

1. Ghastly Kid (2/~/2) OR Unborn Val'kyr (2/~/1)
2. Creepy Crate (1/~/2) OR Fossilized Hatchling (2/~/2)
3. levelling pet

Step 1: Begin with Ghastly Kid/Unborn Val'kyr. Cast Haunt on Gladiator Murkalot.
Step 2: Select your Levelling Pet, but don't attack; switch immediately to Creepy Crate/Fossilized Hatchling.
Step 3: Use BONESTORM on cooldown, and Creepy Chomp/Bone Bite as a filler until you can BONESTORM a second time. Then keep spamming Creepy Chomp/Bone Bite until the your pet dies. (If your pet gets stunned, simply pass the turn)
Step 4: Switch back to Ghastly Kid/Unborn Val'kyr and spam Diseased Bite/Shadow Shock until the fight is won.

Thanks to everyone for the up votes, I am glad the strategy worked for you!

Supremely easy 2 pet with [npc=71163](2,2,2) and [npc=64352](2,1,1):

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• Start with your [npc=71163]
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• [petability=218]
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• Spam [petability=422]
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• [petability=218] as long as the enemy doesn't have blocks or shields up
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• Spam [petability=422] till death turn, then use [petability=321] (again ensuring no shields, but not vital, as you will kill all 3 with or without ascension, just makes it a bit quicker with)
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• Bring out levelling pet
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• Immediately switch to [npc=64352]
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• [petability=564] when he flies up
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• [petability=369]
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• [petability=449] and [petability=564] till its dead
  You might need to land the last hit with your levelling pet, but it should be nothing at all, only if you get very unlucky too
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Tarr offers some Blizzcon pets against you and while they have some annoying abilities, countering them it's rather easy with smallish chance of RNG messing things up even if you have lowbie pet in your team for leveling purposes or if you are going for An Awfully Big Adventure. For the achievement you don't actually have to use the [npc=82464], it can just hang around in team without ever participating the battle, but not in this case.

I found the following Undead pets effective against him (though Shadeling alone can almost handle all of the opponents):

[npc=61375] (#9 H/S is needed to outspeed Tarr's pets) with

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• [petability=422]
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• [petability=214]
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• [petability=764]
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and [npc=68656] (or pretty much any Undead pet will do) with

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• [petability=648]
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• [petability=212]
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• [petability=780]
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Lowbie requirements: 620 HP (930 if the pet is a Dragonkin)

The course of the battle:

1. 
   
2. Start with [npc=82464] or your lowbie to soak the [petability=1106] from [npc=87976] (needs at least 620 HP from your lowbie pet to soak it, hope it doesn't crit!).
3. 
   
4. Swap to Restless Shadeling while Tarr swaps in [npc=87975] and then cast [petability=214].
5. 
   
6. Cast [petability=422] before Deathy stuns you and pass your next round.
7. 
   
8. Use [petability=764] to avoid Deep Breath (!).
9. 
   
10. Drop one or two [petability=422]s to finish off Deathy.
11. 
    
12. When Tarr brings Murkalot to field, cast [petability=422] again.
13. 
    
14. Your DnD removes the block from [petability=1101] so use Shadow Shock once more. Shortly after Murkalot craters on you - again.
15. 
    
16. What you do next turn is indifferent because [npc=87972] still has block left from Shieldstorm. Just don't use Phase Shift. :)
17. 
    
18. Next part is crucial to the outcome of the battle. Refresh your [petability=214] and pray Jebus that Murkimus' [petability=158] doesn't crit. If it does, winning will become a bit harder.
19. 
    
20. Cast Shadow Shock and then Phase Shift to avoid [petability=761] from Murkimus.
21. 
    
22. After the next two Shadow Shocks your Restless Shadeling will unavoidably die, but you should still be able to finish off Murkimus during your Undead racial.
23. 
    
24. Whether Murkimus is still alive or not, Bone Spider can easily deal whatever is still standing. If Murkimus is still alive and you want to play it safe, use [petability=780].
25. 
    

Last tested to work in build: 19243