The Tempest Staff is an aerial ranged Hardmodesummon weapon. It spawns a small Sharknado minion that follows the player for an unlimited amount of time, and attacks enemies automatically by firing Mini Sharkron projectiles which splatter against enemies and blocks. Its attack is akin to a miniature version of Duke Fishron's tornado/shark attack. The Tempest Staff has a 20% chance of being dropped by Duke Fishron.
The Tempest Staff's tornado moves to intercept enemies at significant range, and can pass through blocks. The tornado itself also damages enemies on contact.
Its best modifier is Ruthless. The Mythical modifier provides the widest array of stat bonuses, but these primarily affect the initial summon rather than the resulting minion. Additionally, minions cannot deal critical hits. The only lasting advantage a Mythical Tempest Staff has over a Ruthless one is knockback.
Tips
Even though the sharks deal a lot of damage, they are not very accurate due to slightly arcing mid-flight. They sometimes fail at hitting quick enemies. Despite this flaw, the Sharknado itself is non-solid (can pass through all blocks) and attack enemies outside of the player's sight.
As the tornado itself deals damage to critters, take care when using the staff while catching them.
They are somewhat useless in small areas because they hover over the player's head. Consider using the Optic Staff because the eyes will hover and hit solid blocks.
Trivia
This weapon is a reference to the 2013 American sci-fi disaster film Sharknado, which features a tornado filled with sharks.
Even when PvP is turned on, like all other summons, Sharknadoes will not attack players.
Summoned Sharknadoes will turn translucent when passing through blocks, similarly to what Duke Fishron and Pigrons do.
The Tempest Staff has the second highest base damage of all summoning weapons, beaten only by the Staff of the Frost Hydra.
The Tempest Staff displays an odd tooltip on the Old-gen console version: 1 minute duration. This is a bug, and the Sharknadoes will follow the player indefinitely.
It is the only weapon dropped by Duke Fishron that does not have its color scheme.