Ballistas in Elden Ring: Nightreign are siege-style ranged weapons that can deal enormous damage at long range. Best used against large enemies or groups, they are slow to reload, and require good positioning. They can be ideal support weapons for any build.
NightreignBallistas - Nightreign Wiki

Hand Ballista
Ballista • Lvl Required 3
Weapon Skill: Kick
Push an enemy back with a high kick. Effective against enemies who are guarding, and can break a foe's stance. Sometimes a simple tool is the most effective.
An unconventional ballistic device modeled on a weapon used to besiege castles. Only capable of firing greatbolts. Perfect for reckless acts such as storming a castle or facing an entire army alone.

Jar Cannon
Ballista • Lvl Required 7
Weapon Skill: Kick
Push an enemy back with a high kick. Effective against enemies who are guarding, and can break a foe's stance. Sometimes a simple tool is the most effective.
Jar cannon which uses explosives to fire greatbolts. Deals great damage but is slow to reload. Experimental firearm brought to the assault on Volcano Manor, where it was discovered that no one knew how to use it.