Can be further augmented with Adds "Enhances 'Dark Seal' effect" via Magian Trial 4989
Enhances Dark Seal effect by increasing duration of Dark Magic by 10% per merit level, including Dread Spikes and Absorb Spells but not Drain II's additional effect.
Trial 4989: 20,000 XP in Dynamis - Xarcabard or Dynamis - Tavnazia with item equipped.