Lightning Aura Rod

All three tiers come from the Tavernkeep in exchange for Defender Medals, which only drop from the Old One's Army. The cane unlocks after any mechanical boss and the staff after Golem, so what you can buy tracks your progression rather than the size of your medal pile.

Owning one is not the same as being able to swing it. Until the event has been cleared at least once, these weapons only function inside the event itself. Finishing it on any difficulty flags both the world it happened on and the character who did it, so a cleared world lets any character use auras there, and a character who has cleared it anywhere can use them everywhere.

Inside the event there is a second resource. Etherian Mana dropped during the fight lets you place additional auras that stay up until the event ends, well past your normal sentry cap. It cannot be carried out or used for anything else.

This is not a turret that shoots. It is a column of electricity anchored to the ground with an orb floating above it, and anything standing inside the column takes repeated hits. No aiming, no travel time, no projectile to dodge.

It also ignores enemy defense outright for effectively everything you will ever fight. That is why a weapon with almost nothing on its damage line still kills things at a good rate. Raw armor piercing matters far more than the printed number once enemies start carrying real defense.

The high hit rate makes it excellent against worms and other segmented enemies, since every segment inside the column counts separately. It also deletes some hostile projectiles, because a handful of them are technically enemies with a single point of health.

The column needs vertical room. Summon it somewhere shorter than its full height and it shrinks, and the orb ends up buried in a block. That is the real problem, because the orb needs line of sight to whatever is in the column, and a buried orb can only reach what is directly beneath it. Platforms shorten the column without blocking sight, so an arena built from platforms keeps the aura working where solid floors would ruin it.

Auras also refuse to share space with other Tavernkeep sentries. You can drop other sentries first and raise an aura around them, but you cannot place one inside an aura that already exists. Put the auras down last when you are clustering.

One more oddity: they slide. On sloped ground, particularly the tunnels of the Underground Desert, an aura can drift a long way from where you placed it, into a wall or right off the screen.

Monk armor and Shinobi Infiltrator armor both shorten the attack cycle and give auras a fixed chance to crit, which sentries do not otherwise get. That crit roll is separate from the one whips grant, so the two are independent events rather than one added to the other.

The Shinobi set also widens the column at both ends, raising the maximum and the minimum, which softens the low ceiling problem in cramped arenas more than anything else can.

Whip tags only apply at half strength here, a deliberate tax for the hit rate and the armor piercing. Do not build a whip rotation around auras expecting the usual return on it.

Take Fabled on the lower two tiers, though Ruthless lands on identical numbers there because of rounding. On the staff go Ruthless outright: the armor penetration is already total and the tag damage is halved, so straight damage is the only thing left to gain.

Dropping an aura next to one of the portals during the event will kill or badly weaken most of what walks out of it at the lower tiers, which is the cheapest way to hold a lane while you deal with something else.