In this work I provide an analysis of Demonic Negation (DemNeg; McCloskey 2009, 2018), a left-peripheral emphatic negator which is found in Modern Irish. The purpose of this case study is to clarify the syntactic and semantic relation between sentential polarity (De Clercq 2020) and Focus, a relation which has been claimed to exist in recent research, and to describe a peculiar strategy for the realisation of Irish negative fragment answers (NFAs). I propose that DemNeg is an overt realisation of negative sentential polarity, and that it sits in the left-peripheral NegP/PolP proposed in the previous literature. I further argue that this projection is found above FocP. A’-movement of an XP to SpecFocP can optionally occur below DemNeg, giving rise to the two possible configurations of this construction (‘bare’ DemNeg and DemNeg+XP). Irish NFAs are derived from the latter configuration via PF-deletion of the material following Foc°, in line with an analysis of NFAs as fully sentential structures (cf. Merchant 2004). I present supporting evidence for my proposal coming from the prosody of Focus stress, the position of Topics, and the form of Irish cleft sentences. I consider two predictions of my analysis (semantic variability in the interpretation of DemNeg as scalar vs contrastive, and licensing of polarity items) and demonstrate that they are borne out.