(Quick Effect): You can discard this card; add 1 "Thunder Dragondark" from your Deck to your hand. If this card is banished, or sent from the field to the GY: You can add 1 "Thunder Dragon" card from your Deck to your hand, except "Thunder Dragondark". You can only use 1 "Thunder Dragondark" effect per turn, and only once that turn.
Discard effect can only search another copy of himself.
Thunder Dragons’ playstyle revolves around discarding and banishing their monsters to trigger their effects. Their monsters almost fully consists of high-leveled monsters so Thunder Dragonhawk and Thunder Dragonroar are important for field presence.
A good setup card for a Thunder Dragon deck. Thunder Dragon Discharge will let you banish Thunder Dragon monsters from your deck to trigger their effects. You can then retrieve the banished monster by discarding Thunder Dragonroar.
Thunder Dragons Hundred Thunder is a generic support for Thunder monsters, allowing you to Special Summon all copies of a monster from your graveyard. Because the Special Summoned monsters are banished when they leave the field this can trigger the effects of Thunder Dragon monsters.
Aloof Lupine does not have anything to do with Thunder Dragons but his effect is very useful to them. Banishing and triggering the effects of 2 Thunder Dragons upon summoning, and adding a banished Thunder Dragon to your hand makes him a great setup card.
Thunder Dragon decks being composed of LIGHT and DARK monsters get access to these monsters who specialize in banishing. Banishing Thunder Dragons as their summoning cost will also trigger the Thunder Dragons’ effects.
Not entirely pointless. The discard effect thins your deck and allows it to be revived for Synchro material with Citree or Dragonhawk, which can then trigger Dragondark's search effect.
You can also banish Dragondark with Gold Sarcophagus/Aloof Lupine/WLC for the search effect, or use those cards to banish Dragonroar to summon this and set up a Synchro like Quariongandrax using Deep Sea Divas.
Can't disagree with you, but those strategies are forced and the cards are not intended to be used that way. This is simply another of those archetypes introduced by Konami which are left there with no good support, at least for now. Just look at the Goyos or the Cyber Dragons, you can run a deck with them but nothing meta worthy.