Exploring Space and Time with Antumbra, Shadow of the Cosmos in Sepulcher of the First Ones

wowhead.com:

Continuing our showcase of unique items from Patch 9.2's upcoming Sepulcher of the First Ones raid, we have Antumbra, Shadow of the Cosmos, a special caster dagger which stacks speed and versatility. Obtained from Rygelon, the celestial Constellar serves as penultimate encounter before facing the Jailer and drops gear which is seven item levels higher than the first eight raid bosses. This is the high item level caster weapon, which can also be used by certain healer specs in the raid.

Antumbra is also visually similar to Algalon's Starshard Edge.Singularity Supreme works in two ways, initially stacking a speed and versatility buff with each offensive spell cast. At 20 stacks, the bonus speed and versatility is doubled for a set amount of time. With the absence of any chance to proc mechanics, this allows the dagger to work on a predictable cadence, which attentive players could time to align with cooldowns, add spawns, or important burst damage phases.

Interestingly, only offensive spells will proc the effect, and so while there is nothing stopping a healer from using the dagger, they would have to work other spells into their rotation to take advantage of it — healers have another option however, in the Genesis Lathe. There are various tints of the weapon, not all of which may be obtainable in game. The final four seen here are earned from LFR through Mythic difficulty raiding.