Insight is a Unique Runeword Unique (crafted onto a Common white base in the Horadric Cube) in Diablo IV Season 15. It comes from Crafted: Season 15 Legacy Runeword in the Horadric Cube (not a drop).
Unique power
Legacy Runeword unique - see S15 runewords topic; one guide lists the guaranteed affixes above.
Affixes
Weapon Damage (+207 - 345)
All Stats (+300 - 360)
Fury Regeneration (when crafted on a Barbarian) (+30)
Critical Strike Damage Multiplier (x200%)
Where it drops
Crafted: Season 15 Legacy Runeword in the Horadric Cube (not a drop)
Details
Slot
Weapon (Multiple Types)
Item type
Runeword Unique (crafted onto a Common white base in the Horadric Cube)