Sylvanas is a newer Undead unit, and this is a solid build using Black Arrow.
Ghoul: Tank to place in front of Sylvanas along with Stonehoof.
Necromancer: Good for pressuring any area of the map.
Stonehoof Tauren: Great tank.
Whelps: Amazing mini that can counter units and help control the map.
Quilboar: Chest opener and good support unit to take damage for Sylvanas a nd Huntress.
Huntress: High damage unit for destroying and pressuring.