Thundercloud
サンダー系魔法効果アップ [thunder kei mahou kouka up] or 'thunder type magic effect up' in Japanese.
A Realm Reborn

Type: Class Trait
Learn: THM28
Description: Grants a 10% chance after each damage over time tick to cause the next Thunder, Thunder II, or Thunder III to add its full damage over time amount to its initial damage, have no cast time and cost no MP
Other: Thundercloud effect lasts for 12 s from being triggered, or until used
Category: Ability