Feint's Siphon: Lunges at a target hero, dealing damage. Passively grants bonus Movement Speed and Agility and siphons a portion of the enemies damage, which temporarily adds to his own.
Soul's Sight: Assumes a ranged form, dealing additional damage based on his Intelligence. Also spawns an eye that grants clearvision in an area.
Essence Shift: Mimics the target's primary attribute and adds a percentage of that stat to his own until either he dies or Essence Shift is used again.
Shadowblade may seem like a pretty confusing concept. Think of him as a hero with a Steamboots-like ability to switch stats on the fly, with each form granting additional bonuses and a different type of spell. It's still not entirely clear how the form-switching works and what the hotkey setup is, but the Hero Spotlight video gives us at least some idea of what each ability does.
Gargantuan's Blast is a basic AoE nuke and slow effect, but one thing to note is its zero cast time. As shown in the video, it's also very effective as a reactive damage reduction spell.
Feint's Siphon is a single-target leap ability, with the added bonus of temporarily stealing damage from other heroes. This gives him some potential as a carry, especially when fighting against other carries.
Soul's Sight seems to signal an alternative, Intelligence-based build for Shadowblade, giving him a ranged attack and bonus damage. The clearvision spell will no doubt be useful, no matter which attribute Shadowblade focuses on.
Essence Shift again allows you to take advantage of opposing carries by granting a scaling amount of the target's primary attribute. It's also key for switching your primary attribute in a pinch.
Shadowblade certainly seems like an interesting hero. The style of play appears to be hyper-dependent on how the player builds it, with respect to their own team and the opposing team's lineup. Do you want to focus on ganking and leveling up the AoE slow and the leap abilities? Do you focus on the ranged form to allow better last-hitting and harass in the early laning phase?
This versatile hero becomes available in tomorrow patch, which will include several big changes!

Links
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