Abyssion in Terraria

If you searched Abyssion in Terraria, the current name is Forgotten One. The Thorium boss list says the old name “Abyssion, The Forgotten One” was renamed Forgotten One. It is a Hardmode boss after Plantera, fought in the Aquatic Depths.

How the summon works

Kill Aquatic Hallucinations in the Aquatic Depths. They drop Abyssal Shadows. Each one you pick up adds a stack of False Presence. Three stacks summon the boss. After the first kill, an Abyssal Shadow becomes an ordinary summon item. Right-click False Presence to cancel a stack you did not want.

Numbers and phases

From 85% life it shells and each hit removes 1 life. At 50% life, or 66% on Expert, the shell breaks. Expert adds a third phase at 33%. Leaving the water enrages it, in the same spirit as Plantera. Drops include The Incubator at 16.67%, plus Mantis Shrimp Punch, Trench Spitter, Old God's Vision, Siren's Lyre, and Whispering armor at 16.67% each, and R'lyeh's Lost Rod and the trophy at 10%; the mask is 14.29%.

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