Squid Ink is one of those deep, near-black inky blues that doesn't want to be a feature wall — it wants to swallow a room whole. Use it drenched. Walls, woodwork, ceiling, the lot, ideally in different sheens: a soft eggshell on the walls and full gloss on the woodwork. That sheen shift is what gives you the depth — the gloss catches light and the matt absorbs it, so the room reads rich rather than flat.
For accents, think aged metallics and jewel tones rather than contrasts. Tarnished brass, antique gold, a deep burgundy in an armchair or velvet curtain — those sit beautifully against this kind of inky base. One rich note is enough; don't go scattering five colours about.
Where you need a lighter break, don't reach for white — it'll look harsh and chalky against Squid Ink and break the spell. Go warm and putty-ish instead. Mylands Alderman No.60 (LRV 58.8) is a lovely mid stone that grounds the scheme without fighting it, working as adjoining-room or skirting contrast. If you genuinely need a pale, keep it soft and warm: Paint & Paper Library Sand I (LRV 95.4) or Dulux Moon Shimmer (LRV 92.3) both carry enough warmth to feel like candlelight rather than cold daylight against the dark.
The "but it'll be too dark" worry is the usual one. In a north-facing room with poor light, yes — accept that it'll be a cocoon, a snug or a moody dining room, and lean into it with warm lamplight rather than fighting it with overhead spots. In a south-facing room it comes alive in the evening and stays handsome by day.
Practical tip: test the gloss woodwork before you commit. Full gloss on a deep colour shows every imperfection in the prep, so the surface needs to be sanded properly and primed flat. Get that right and Squid Ink looks like money.