Removing:

Helvault is too efficient, especially compared to similar cards like Altar of Shadows and Predator, Flagship.

Baneful Omen, Flooded Shoreline, Dispersing Orb, Ephara's Warden, Stymied Hopes, Vine Kami, and Venerable Kumo are too weak and rarely make it into decks.

Adding:

Adding Where Ancients Tread as a buildaround. Including Viashino Cutthroat, Leyline Phantom, and Pangosaur as repeatable enablers.

Increasing black's interaction with combo by adding some discard spells in Mind Warp and Extortion.

Adding Searing Touch to help support Sphinx-Bone Wand and Deep-Slumber Titan.

Experimenting with a Mercenaries archetype.