Looks to me like a black sun coral.
Care Level: Moderate
Temperament: Peaceful
Lighting: Low
Waterflow: Medium
Placement: All
Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Color Form: Black
Supplements: Calcium, Strontium, Trace Elements
Compatibility: View Chart...