Mutant Massacrer is a Legends of Idleon achievement: 2 rewards. Defeat both Mutant Minibosses, the W3 Slush and W4 Mush. You must defeat Slush before Mush, in that order.

Mutant Massacrer | Idleon Toolbox

Defeat_both_Mutant_Minibosses,_the_W3_Slush_and_W4_Mush._You_must_defeat_Slush_before_Mush,_in_that_order.

Mutant_Massacrer

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Mutant Massacrer

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