Ballista Rod

All three tiers plant the same thing: a stationary crossbow that appears on the nearest ground under your cursor and shoots heavy bolts at whatever comes near. It fires slowly and hits hard, and each bolt punches through a few enemies before it stops. That piercing is about lines of enemies rather than about damaging one target faster, since a single bolt cannot hit the same enemy twice.

The Rod is available from the Tavernkeep straight away. The Cane unlocks once a mechanical boss is down and the Staff once Golem is, and all three are bought with Defender Medals rather than coins.

You cannot use any of these outside the Old One's Army until you have finished the event at least once. Completing it flags both the world and the character. A world that has seen a completed event lets anyone who visits use them anywhere in it, and the character who finished it carries the ability into any world, including a brand new one.

During the event itself, Etherian Mana dropped by the waves lets you plant extra sentries well past your normal limit, and those stay up until the event ends. The mana is worthless outside it, so there is no reason to hoard any.

Squire and Valhalla Knight set bonuses do not just add damage, they change how the sentry works. Bolts fly noticeably faster and pierce roughly twice as many targets before dissipating, and taking a hit grants Ballista Panic for a few seconds, which speeds up the reload. Valhalla Knight shortens that reload again by itself, so wearing it with the buff running turns a slow siege weapon into something close to sustained fire. Getting hit becoming a good thing is the odd part of playing this build, and it pairs with Valhalla's healing to make standing in the fight the correct choice.

Ballistas lead badly against anything quick, and flying enemies during the Old One's Army will drag their aim away from the ground wave. The fix is to stop thinking about aiming and start thinking about lines. Put them where enemies must walk through the shot path, which usually means behind the portal rather than in front of it, so the bolts land across the route rather than chasing what has already arrived.

The standard event layout is Lightning Aura sat on the portals themselves with Ballistas covering the middle ground. Outside the event, a good arena and Valhalla Knight makes them strong enough to carry boss fights well into the endgame.

Fabled is the one to roll. Once your summon damage bonuses climb high enough, including whip tags, Ruthless overtakes it on the Staff specifically.