About the hero: Arborus is a hero with deadly burst damage on his skills, even if you don't build AP, you'll still giving a Deadly damage for non-tankers enemies.
you've a strong engage, with your W skill and if you combo RWER it'll be very hardly for a non-tanker hero survive.
Arborus' ultimate is a charging skill, so... the most of time you take to explode, more will be the damage, one of strategies is stay out of enemy sight charging your ultimate then engage with your W, then burst your target with your all skills.
Arborus has a strong gank, your W roots your enemy on the ground, then you can go to his back and use your Q to pull he to your team side.
After his ultimate, his E skill is the main source of damage of arborus, it have 2 instances of damage, hitting and explosion. try always to hit your enemy, cause your skill will follow him no matter the distance and then explode.
I'll talk about arborus skills now.
Q) Arboreal Spin.
A spin attack that knocks back surrounding enemies 650 radius, dealing magic damage.
Consumes 90 mana. 10 second cooldown.
Effective range: 450
Magic damage: 70/140/210/280
W) Thrusting Timber.
Rush to the enemy, stunning them and dealing magic damage.
Consumables 80/90/100/110 Mana. 12 second cooldown.
Magic damage: 100/150/200/250
Stun time: 0.75/1/1.25/1.5 seconds
E) Sapling Explosion
Hurls a sapling at target area, dealing magic damage to all affected enemies. The sapling will follow nearby enemies and explode, dealing additional magic damage.
Sapling exists for 35 seconds.
Consumables 95/105/115/125 mana. 10 second cooldown.
Effective range: 300
Hurl damage: 75/100/125/150
Explosion damage 80/130/180/230
R) Nature's Vortex
Reduces damage taken by your allies. When Nature's Vortex ends, all enemies in the area of effect suffers magic damage. Use again to preemptively cast Nature's Vortex.
The longer the spell is charged, the higher the damage. The spell can be charged for a maximum of 5 seconds, and after charging you have 2 seconds to release it.
Consumables 150/225/300 Mana.
Effective range: 800
Max Damage 500/650/800
Damage per second 100/130/160
Allie's Damage Reduction 25%
Order of skills: Before i give my order, you must have in mind you need to have in mid what kind of style you'll play, so i'll put 3 kinds of order for different styles.
As Mid Laner: E/W/E/Q/E/R/E/W/W/W/R/Q/Q/Q/STAT/R/STAT/STAT
As Jungler/Ganker: E/W/Q/E/E/R/E/W/W/W/R/Q/Q/Q...
Pros: Protect his team from heavy damage with his ultimate.
Gives massive area damage.
Have a strong control and is a great hero to focus enemies' MVP.
Very strong engage. Grows in mid game and stills strong in late game.
Cons: Low Armor and life if your priority is damage, hard to escape, can be disabled on his W becoming very vulnerable.
Synergies and Counters:
Synergies: Jeanne/Angelus: Those heroes have skills to keep enemies on area, whose you can burst with your ultimate, dealling a huge damage.
Tiamat/Lulu: they can help you to engage on enemies, tiamat can protect you with his ultimate, allowing you to enter in fight and charge your ultimate dispersing enemy's team.
you can engage while tiamat's ultimate is in charge helping him to enter inside enemy's team easily helping on CC. Lulu can boost your speed then you can use your R and run fast toward enemy's team arriving with almost of your ultimate charged.
Titanus/Daji: 2 heroes who also have to charge their ultimates to give more damage, titanus ultimate slows enemies and give a stun. helping you to finish them with your R too, and Also titanus have slow, snare, you have snare too, is a very annoying duo.
Daji like arborus, have a charging ultimate, so when she activate her ultimate she'll be focused, you can help her to take less damage, then her ultimate will stuns all enemies in area, it's a nice combo with your ultimate.
Poseidon: i guess this is one of the most powerfull counters to arborus, he can escape even your W skill and your R damage using his W, and he can uses his ultimate to completaly shut down your ultimate power damage, destroying your game and utility in match... poseidon is very very annoying to your gameplay.
Lotus: Another annoying counter to you, she can ult holding you far from her team, she can disable you with her E, finishing with your game too.
Saya: Like Lotus, she can hold you far from her team with her E, giving you a hard time to use your ultimate properly.
Diana: Like Poseidon, Diana is the second annoying hero aganist arborus, she can escape he easily not one, or two but three times, because she have a dash with invisibility to run away after your engage, she have her Q to snare you into ground, and she have the second shoot of Q, knocking you back destroying your ultimate damage on team fight too.
Hades/Medusa/Sylvana/Lunaria: It's more because of their silences, it's the weak point of arborus, if he's silenced, he's nearly useless hero.
Alternative CD Reduction build
Consideration: You can also do Jade's heart if the other team has a lot of CC skills like stun, to difficulty your engage and ultimate's damage.
You can also try etheral boots if enemy's basic attack damage team is too much heavy, to reduce your damage taken.
You can also try Divine to boost your burst damage power. And you can also change your arcane orb for others itens if in your team already have a ally with this item.
Well i hope you enjoy my guide, i don't know how to use this thread properly but next time i hope i do a better guide.