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

Arachnoid
The pre-1.0 wiki text for this skill gives numbers the 1.0 files changed, so it is not shown; the 1.0 values are above.
Where Arachnoid sits on the 1.0 tree
In the Ranger area. The cheapest way in from a starting point buys 3 nodes for 3 points, this one included (one rank each).
Related Ranger skills
Same archetype — likely candidates to slot next to Arachnoid in a build.
Airborne1pValues in the 1.0 files: 12% per rank, 3 ranks.
Backstab Mastery1pValues in the 1.0 files: 20% per rank, 3 ranks.
Blessed Arrows1pValues in the 1.0 files: 8 per rank, 3 ranks.
Counter Battery1pValues in the 1.0 files: 8% per rank, 3 ranks.
Dexterity1pIncreases your Dexterity attribute by 1 Increases Bow and Dagger damage by 5% per Attribute Point
Eagles Bane1pDamage against flying enemies increased by 30%.
Endurance1pIncreases your Endurance attribute by 1 Increases Stamina by 10 per Attribute Point
Inner Fires1pMaximum Shroud Time increased by 2 minutes, allowing you to explore for longer. Shroud Time Should this time run out, the Shroud will consume you.
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.