Thunder IV (サンダーIV, Sandā IV?) is a recurring ability in the series. The ability first appeared in Final Fantasy XI as a Black Magic spell, but has reappeared in certain spin-off titles as an ability for Final Fantasy XI-related characters and monsters.
Despite sharing the name in the English localization of Final Fantasy XIV, the abilities known as Thunder IV in the title are in fact the recurring Thundaja spell in Japanese.
Template:FFXI Spell Thunder IV is a tier IV Black Magic spell that deals lightning-based elemental damage to a single target. Thunder IV is available to Black Mages, Geomancers, and Red Mages. Scholars are also able to use this spell while under the effects of Addendum: Black or Enlightenment. Additionally, a Summoner's Thunder Spirit and certain setups of a Puppetmaster's Automaton are capable of casting this spell.
Blood Pact: Rage
Thunder IV is a level 60 Blood Pact for Ramuh. It can be used when the Summoner or Ramuh (or both) is Silenced. Amnesia on either the Summoner or Ramuh prevents the use of Thunder IV. Ramuh's TP is consumed upon using this ability, boosting its power. However, TP is not needed to use this ability.
Thunder is the sound caused by lightning. Depending on the distance and nature of the lightning, thunder can range from a sharp, loud crack to a long, low rumble (brontide).