Level 95 Companion: Prowling Chimeral Smith of Kitava^0.3

Notes

League start and leveling:
First thing you should do is mule over a scepter from the witch.  Your base scepter doesn't really matter, later on you want a Purity of Fire Shrine scepter but anything will work in the early acts.  You should also cut Skeletal Sniper and Flame Wall into your first set of level 1 gems.  
Once you get some more spirit from the King of the Mists , take as many snipers as possible and spam their gas arrow.  Using Fire Attunement and the flame wall should make igniting your gas arrows fairly easy.  
I take this setup all the way to level 31 where I can then swap to Companions.
Once I hit 31 I swap gear and passive tree to make sure I have enough dex as well as Vile Mending and Crystalline Flesh so my beast doesn't immediately die from the Infernal Legion support.  The Companion should do great damage out of the gate but I keep my snipers around for extra burst damage on single target.  My favorite Companion that is farmable is the Prowling Chimeral, you can catch them in the Chimeral Wetlands but the farm is... tedious to say the least.  The easiest farm for a good beast is one of the Boars from the Infested Barrens.  Finally, most people have a good time with the Frozen Mandibles ant companion you can farm in the Interlude.  We have a guide on this on the YouTube channel.  
For first and second ascendancy take Coal Stoaker and Life/Regen/Fire res or Phys as Fire for your chest.  You can wait until around Act 4 to take your 2nd ascendancy if you have pretty solid gear or until you find a decent base type.  You generally don't find anything too impactful until you start getting chest armor with implicits (Ornate Chest) until maps though.

Infernal Legion Companion Smith FAQ:

Q. Why Smith?
A. I prefer to play SSF and HCSSF (or GSF) and Smith allows you to res cap and build a fairly tanky character at basically no cost.  It's probably not the best class for IL Companion builds but it's my favorite.

Q. My Companion keeps dying, what do I do?
A. First thing is make sure your Companion has as close to 90 Fire res as possible.  This can be achieved by catching a beast with the "Fire Resistance" mod and taking the Crystalline Flesh node up by witch, or taking Crystalline Flesh along with the max fire res passive nearby and the Living Death notable with surrounding max fire res passives as well.  Additionally you can add a Skeletal Cleric to provide healing to the Companion.  

Q. I am not doing a ton of damage, how can I improve that?
A. Upgrade your gear is going to be the easiest solution here.  Buying or crafting 20% companion life/20% Companion damage emeralds is a massive boost, getting as many +minion levels on your helmet, amulet, and scepter, and adding a Saitha's Spear for aggravated ignite will basically double your damage.  You can also try to farm a beast that has the "Extra Fire Damage" mod, but this could take a while depending on which beast you choose.

Q. Why are you STR stacking?
A. Warrior has a ton of access to STR nodes on the tree, combining that with the Sturdy Ally notable gives both our character and our companion a ton of extra life which means more damage and survivability.  

Q. You said you were using Carrion Call in the build during the 0.20 video, what changed?
A. Two major reasons, first off it's way harder to get max all res now with the changes to the tree, and the fact that we started on GSF with limited access to uniques