Make them spend the dash, then cash E2: use E1 to get into contact, weave the passive auto, and let W be the health-swing spell after they commit movement instead of throwing full combo on first touch
Path for the ult you want: jungle Sylas is strongest when the next lane, river fight, or countergank is chosen around the stolen button that will solve it, because Hijack changes your actual job from fight to fight in a way other AP junglers do not get
Sylas pays unusually hard for begging the map from a bad clear, so if the opener does not give you real contact, reset for the fast component instead of forcing a raw-chain gank from low health and arriving to the next fight with only one thin spell cycle
In game, sort stolen ults by the job they solve right now, not by highlight value. The best ones either start contact for you, keep someone in range long enough for passive autos and W to matter, or give you a clean second cast of threat after your base combo. Reliable engage, hard lockdown, and teamfight buttons are usually worth more than flashy damage if they let you choose when E2 lands. If the enemy comp gives you weak steals, stop hunting for the perfect one and take the ult that makes the next skirmish simplest. Sylas gets a lot from certainty.
After casting a spell, Sylas stores a charge of Petricite Burst. Sylas's basic attacks will expend a charge and whirl his energized chains around him dealing bonus magic damage to enemies hit. While Sylas has a charge of Petricite Burst, he gains attack speed.
Sylas lashes his chains out, intersecting at his targeted location dealing damage to and slowing enemies. After a delay, magical energy explodes from the intersection point dealing damage.
Sylas lunges at an enemy with magical force dealing damage and healing himself against enemy champions.
Sylas dashes to a location. Sylas can recast the ability to throw his chains out, pulling himself to an enemy he hits.
Sylas steals the enemy's ultimate ability and can cast it freely.