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

Shroud Filter
Dealing magic weapon damage has a 15% chance to trigger a small flame burst that restores 30 seconds of Shroud Time to you and your allies within 20 meters. Shroud Time Should this time run out, the Shroud will consume you.
Related Mage skills
Same archetype — likely candidates to slot next to Shroud Filter in a build.
Arcane Deflection1pOn a successful parry, gain 20 mana.
Counterstrike1pThis magical attack can trigger other skills.
Eternal Spark1pValues in the 1.0 files: 15% per rank, 3 ranks.
Fire Resistance1pIncreases your Fire Resistance by 5% which reduces the amount of Fire damage received.
Healer1pValues in the 1.0 files: 15% per rank, 3 ranks.
Healing Revive1pValues in the 1.0 files: 8% per rank, 3 ranks.
Ice Resistance1pIncreases your Ice Resistance by 5% which reduces the amount of Ice damage received.
Intelligence1pIncreases your Intelligence attribute by 1 Increases Magic 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, effects and tree position.