The crystal maiden, the walking geode, incredibly annoying to farm - Citrine!
Release date: 2023-02-15
Passive: Citrine emits a healing aura within a radius of 50 meters that continuously recover a base 5 Health points per second. Whenever she picks up a regular Health Orb, Dispensary produced Empowered variant, or Transmutation Probe converted Universal Orb, regeneration rate is permanently increased by 0.1 points, up to a maximum heal rate of 25 points per second.
Fractured Blast - Slash and stagger enemies with a crystal blast that inflicts Bleed. Enemies afflicted with this Status Effect have an increase chance of dropping Health and Energy Orbs.
Preserving Shell - Citrine guards herself and nearby allies with a crystalline shell that gradually decays. Kills and assists increase the defensive power of the shell.
Prismatic Gem - Deploy a gem that shoots prismatic beams. The gem targets enemies that are taking weapon damage from Citrine and her allies. Its beams inflict Heat, Cold, Toxin, and Electricity Status Effects. Status Chance and Status Duration increase for nearby allies.
Crystallize - Citrine summons crystal fractals. The fractals rush forward, seeking enemies. Enemies touched by the fractals are paralyzed crystalline growths. Hit the growths to deal Critical Damage.
Acquisition: Pain
Main and component blueprints can be obtained from Rotation C of Mirror Defense Tyana Pass on Mars. Alternatively they can be purchased from Otak in the Necralisk, Deimos with Belric Crystal Fragment and Rania Crystal Fragment.
Alas sonar got capped at only 2 stacks.
Mostly capped at two stacks, although there can be funny business based on how many body parts an enemy has. I don’t think there are any enemies where that’s relevant. Also, the stacks multiply against themselves, so a 200% strength Banshee is actually a 100x multiplier, not a 20x multiplier. Even a 155% strength Banshee yields a 60x double stack.
Not counting things like Secondary Surge Deathtrap Trigger setups, or multiplicative Accuracy Harrow setups, even a single stack of Sonar outperforms Citrine for most weapons and Harrow for some, or for enemies without headshot multipliers. Double stack, I don’t think anyone comes close, not even a hypothetical Sentient Wrath Rhino.