This Vainglory Skaarf build guide is brought to us by the official programmer and designer of the hero named Brett (that's the dude you see in this page.
I like to start with a Energy Battery and some potions and head to the lane. Skaarf is an excellent lane hero because he has a spamable skill shot fireball for harassing and is good at pushing the minions back if they get to your tower. Skaarf likes to spam his fireball whenever it is up, and if you aren't careful you can easily drain your energy. To help with this, I try not to use his goop pool too much early on unless I am going in for a kill or some strong guaranteed harass on the enemy. Focus on last hitting and getting pot shots off with the your skill shot on the opposing laner. Also keep an eye on your junglers. Skaarf has respectable base damage and so provides good damage numbers all game long, which can easily turn an early skirmish in your teams favor.
I don't really have a preference for ability order or overdrives. I Always take Spitfire first, since Goop only slows until you can light it on fire. After that, it is up to your play style. If you're good at landing Spitfire, consider taking its overdrive which can significantly boost the damage. If you like the wave clear power and strategic choices of Goop, overdriving it will give you a significant increase in the duration of the pool as well as a much shorter cooldown. I try to keep both skills at roughly equal levels and tend to take the overdrive that I think will benefit me the most in the current game. Some people even like taking both overdrives and leaving Dragon Breath at 2 levels, which is recommended if you have difficulty using the ultimate to its full potential. His ultimate is the hardest thing in his kit to do effectively, so this might be a good approach until you get some time to practice it and learn when the best situations are for using it.
Item wise, get some energy early and then focus on crystal. Make sure you have some boots so that you have an escape when you need it. If you are doing well and getting kills, getting a Frostburn first is probably your best bet, since it will give you some more CC which will help secure kills and sustain your lead. If you are behind, consider getting Eve of Harvest first to supplement your survivability. Most effective kits include both of these items, but the order you build them is situational. After that, consider buying defense if you are being focused on (like Crucible , Aegis , or Metal Jacket depending on where the enemy damage is coming from), or get a Shatterglass or Broken Myth to boost your damage even more.
Skaarf is an excellent mid game champion. Once you get a Void Battery and start working towards
Frostburn and Eve of Harvest , your damage starts to really shine.
Skaarf is a really good hero to have on your team when taking objectives. While his burn passive does reduced damage to Kraken, it still does full damage to gold and crystal miners, which makes taking objectives a breeze. His pool can also be placed beneath turrets and lit on fire from range to get lots of free damage.
Skaarf is also a good poke champion. He has the only good ranged skill shot in the game as of this writing, so it is easy to harass enemies waiting in the brush to gank you. When you get frostburn, his fireballs can be used to reliably chase down fleeing champions and ensure kills.
But Skaarf's biggest strength is his team fight presence. Goop pools can be placed strategically at bottlenecks and escape paths before a fight starts, and fleeing enemies will be forced to walk through them to get away. Pools don't need to be lit on fire with your fireball or ultimate; any enemy that is on fire will automatically light the pool on fire when they walk through it. The pool not only does damage over time, but the moment of ignition of the pool does a pretty good burst of damage too, so don't forget this. You can always wait until an enemy is already on fire before casting the pool right on top of them for some guaranteed burst.
His ultimate not only deals lots of damage, but also has a lot of utility in it with it's slow and speed boost mechanic. Enemies trying to run away while you are inhaling will be slowed, allowing your allies to get there to help finish them off. Or, while you are exhaling, enemies trying to close the gap are going to be slowed, giving you more time to deal damage and react. But don't forget the ally speed boost on his ult either. It can be used to boost your enemies into battle, like a warhorn that can light things on fire. The inhale can also be used to help your allies get out of trouble and cause enemies to think twice when chasing them, lest they take a flamethrower to the face.
Having said all of this, don't underestimate Fan the Flames . His burn deals damage based on a percentage of the enemies health, so it can be used to deal great damage to even the tankiest opponent. It only starts at 3% health, but it ramps up by 3% per auto attack up to 12% at max. It also lasts for 3 seconds after the last application of the buff.
This means that, for example, if your auto attacks are 1 second apart and you attack continually until you get up to the cap before you stop attacking, you will deal 3% in the first second, then 6% after your next auto attack, then 9%, then 12% for 3 seconds. This adds up to a total of 54% of their health in damage over a duration of 6 seconds. That is without casting any other spells either. Of course, this damage is mitigated by shield, but Broken Myth can help you pierce this shield and get closer to the full effect of the burn.
Up until this point, you might be wondering why you should ever pick anyone other than Skaarf. The fact is that you shouldn't, but even still, there are some things you need to watch out for.
First of all, Skaarf is practically the most vulnerable hero in the game. He has no escape and very little CC. You can drop a goop pool between you and approaching melee enemies, but this won't help you against a ranged champion or someone already on top of you. It is very easy to get stunned out of your ultimate, for which I recommend getting reflex block/crucible.
Glaive can be a problem for Skaarf. His Afterburn allows him to get to you quickly, and can knock you out of your ult before you even get it off. He then pummels you with rocket axe and there is very little you can do about it. Catherine can also cause problems, but she has a bit harder time getting to you than Glaive does and usually doesn't have as much follow up damage. Try not to overextend when facing a Glaive or you might get punted into a group of waiting enemies. And wait until he's already blown his afterburn before starting your ultimate.
Taka likes to take a subtler and often deadlier approach. It is easy to think you are safe at a distance with Skaarf, but you can have your throat slit by a dancing fox at any moment when Taka is in the game. Stay near your team when there is an enemy Taka, and surround yourself with scout traps.
Petal is a different kind of annoying. There is nothing worse than lining up that perfect fireball only to have it blocked by a plant on the ground. Hitting her when she is fleeing is especially difficult because her munions follow directly behind her. It is hard to hit her with damage without using your pool, so make sure you use it effectively to maximize its damage. It is easy to clear petals munions with pools when they are attacking a target, and this is especially damaging against a crystal petal who gets all of her damage from the munions.
Keeping your boots level on par with the enemy team is important, and get Journey Boots when you can afford them. Since Skaarf doesn't have a natural escape, you need every variable in your favor you can get. Frostburn can also help with this, so get it as soon as you can. Skaarf can cast spells frequently, which means he can keep enemies slowed a majority of the time as long as he can hit them. You also should consider mixing some defense in to your build when you can afford it. This can make a big difference when you are getting burst down a lot.