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When you have lvl 6 and Teleport ready go back to base buy what you need to buy and gank BOT with Unstoppable Onslaught,make sure to ultimate when you have the enemy bottom lane in range so you can knockup someone :D , make a kill and then Teleport TOP and continue to farm your Soul Furnace passive.

My favorite combo is Soul Furnace, Roar of the Slayer, Decimating Smash, Soul Furnace (when you dont have lvl 6)
When 6 is ready -> Soul Furnace, Unstoppable Onslaught, Decimating Smash, Soul Furnace, Roar of the Slayer or Soul Furnace, Decimating Smash, Unstoppable Onslaught, Soul Furnace, Roar of the Slayer I prefer to use the first combo :D.
The next combo i use is to keep away the ADC and make him run away from TeamFight Just Flash-> Unstoppable Onslaught-> Decimating Smash-> Roar of the Slayer Him . If you want wait until the enemy group and catch MID/ADC/JUNGLE or TOP with this combo.
With this strategy you win every teamfight and remove the ADC :D.

Now this strategy is very popular with SION.
If enemy will start BLUE go steal his RED with passive(Just hit the RED and wait to die :D)

To clear LANE fast use Soul Furnace, Roar of the Slayer, Decimating Smash, Soul Furnace.

1)If you have Banner of Command use it on cannon minion on TOP and go push with your team MID.
2)You can split push any lane and escape with Unstoppable Onslaught :D.