Tome of Dripping Shadows

This book constantly drips evanescent tendrils of shadow that seethe and writhe. The tendrils have a will of their own, retreating from light sources and curling toward darkness. While you hold the tome, you gain darkvision; if you already have darkvision, you gain greater darkvision instead. Preparing spells from this tome strengthens your shadow magic and gives you a greater understanding of shadow spells you add to this tome. Any shadow spells you prepare from this tome that are at least 2 levels lower than the highest-rank spell you can cast are treated as 1 level higher for the purposes of counteracting them. When you add a shadow spell to this tome, you can prepare heightened versions of that spell up to the highest level of that spell that you are able to cast.

Activate [R] envision

Frequency once per day

Trigger A target of a shadow spell you prepared from the grimoire critically fails a saving throw against the spell

Effect You recall a fragment of the shadow magic that suffuses your target and wrap it around yourself like a caul. The triggering creature's saving throw result is a failure, not a critical failure. For the next minute, you become Concealed to all creatures and you are Hidden from the triggering creature, regardless of what precise sense it has. If you use a hostile action against the triggering creature, you become only concealed to it (rather than hidden) at the end of the hostile action.