Staff of Heavenly Thunder

It needs a Cloudreader Leader. The set’s only Cloudreader Leader is Indra, from the same starter deck (STT05). With Raizan, Piko of Thousand Blades or The Sisters it is a 3-cost +0 and does nothing.

At 4 weapons in your discard pile it is +4 for 3 IKZ: as much as Ikazuchi for 1 less, and 1 more than Tenraku. The count is live, so it grows during the turn as weapons hit the discard pile.

Weapons go to your discard pile at the end of every turn, so arming one card a turn from your first turn gets you to 4 on your fifth turn. Indra’s ability gets there faster: when your top card is a weapon, pay 1 IKZ and discard it. Arashi no Ina can discard three cards at once.

Taking weapons back out lowers it. Surge Gate, Raizan’s Riposte, Wu Cha and Forging Tricks all pull weapons from the discard pile, so in a Staff deck, count before you use them. Your opponent’s Zubi takes up to 2 out too.

Kenta of Many Swords puts five cards in your discard pile at once, and Monk’s Wager, Novice Anji and The Inked Brawler add more. Weapon Toss counts the same pile, and Open Armory equips out of it, so count before you use Armory.