Partly updated for Enshrouded 1.0— 1.0: the unlock cost; the rest is pre-1.0 wiki data

Upwards Slash Attack
When equipped with a Melee weapon, launch a powerful upward strike during the ascent of your jump. Use this skill to rapidly close the distance on flying enemies. Cost: 25 Stamina
Where Upwards Slash Attack sits on the 1.0 tree
In the Warrior area. The cheapest way in from a starting point buys 6 nodes for 8 points, this one included (one rank each).
Related Warrior skills
Same archetype — likely candidates to slot next to Upwards Slash Attack in a build.
Absorb1pValues in the 1.0 files: 4% per rank, 3 ranks.
Constitution1pIncreases your Constitution attribute by 1 Increases Health by 50 per Attribute Point
Finesse1pValues in the 1.0 files: 15% per rank, 3 ranks.
Heavy Handed1pAn enemy's stun bar is increased by an additional 20% when attacking into their block with a melee weapon.
Heavy Plates1pValues in the 1.0 files: 4% per rank, 3 ranks.
Purification1pAfter defeating a Shroud infested foe with a melee weapon you replenish +5 seconds of Shroud Time. Shroud Time Should this time run out, the Shroud will consume you.
Shiny Plates1pValues in the 1.0 files: 4% per rank, 3 ranks.
Strength1pIncreases your Strength attribute by 1 Increases Melee damage by 5% per Attribute Point
Sources: game files 1.0 + Keen Games 1.0 patch notes (changelog, combat changes) for the unlock cost; enshrouded.wiki.gg (pre-1.0) for the description and effects.