Timeweaver Spiders share a basic shape with their evolutionary ancestor, the Phase Spider, but any similarities between these two species ends there.  Timeweaver Spiders are protected by a thin, blueish-grey chitin.  As they get older, they develop patches of a dull waxy color and texture.  It is rare to observe their "natural" coloration, however, as they can shroud themselves in the mist-smoke of the demiplane of time while within their lair, in order to blend in with their web.

Timeweaver Spiders are only found on the demiplane of time, and Phase Spiders are not. Some scholars have speculated that a colony of Phase Spiders might have been caught in the eye of a timestorm while in the middle of attempting to phase to the Etheral Plane together, ending up trapped outside of reality in the demiplane of time instead.  With no way back to reality, they must have struggled to climb the food chain, each generation being warped and molded by the energies of the demiplane of time, until they eventually became adapted natives.  This new species is now found all over the demiplane.

Though they can inhabit any part of the demiplane of time, Timeweaver Spiders favor vortices and gateways, due to the significantly higher traffic that tends to flow through those locations.  These spiders spin their unusual webs here, to trap both native inhabitants and unaware linear travelers for food.  Timeweaver Spiders ignore very large prey, as it would be too dangerous to attempt to capture, and if an Aeon Behir ever happens to crash through a Timeweaver Spider's lair, the spiders immediately abandon it and flee, seeking new ground to settle in.

The most obscure comer of the Timeweaver Spider’s webbing contains the remains of all victims, as well as their possessions. The spiders like to hide these things out of immediate sight to avoid tipping off any would-be dinner guest to the dangers ahead. Still, the spiders understand to some degree the value of many of the discarded trinkets and treasures of past victims. Though they have no use for such things personally, Timeweaver Spiders can be cunning enough to sometimes bait the entrances to their lair with an interesting-looking item or two.

Lair Actions

On initiative count 20 (losing initiative ties), one Timeweaver Spider takes a lair action to cause one of the following effects; the Timeweaver Spiders can’t use the same effect two rounds in a row:

• A Timeweaver Spider hookes multiple threads of mist-smoke webbing and whips them down toward a single target.  The target must make a DC 15 Dexterity saving throw, or suffer effects identical to a Hold Person spell, as cords of temporal energy tangle around them.  The spiders typically then ignore any held creatures, unless all intruders have been held, paralyzed by poison, or slain.
• A Timeweaver Spider may climb onto and then crawl along a strand of webbing.  Mist-smoke swirls around them, concealing them mid-combat.  That spider becomes hidden until the next round.  At the beginning of their turn, any spider hidden in this way can move to and make a sneak attack against any target, becoming visible again in the process.  This attack gains Advantage to hit, and criticals on a 19 or 20.

Regional Effects

The region containing a Timeweaver Spider’s lair is carefully maintained by the spiders that inhabit it, which creates the following effects:

• A Timeweaver Spider's lair is a great tangle of webbing, made of long strands of mist-smoke.  This webbing blends in so perfectly with the omnipresent mist-smoke of the demiplane of time that it is all but invisible without magical aid (Detect Temporal Anomaly illuminates the webbing like burning rope).  This webbing is not sticky, nor even physical, like other spider webbing.  Instead, any creature other than the spiders who comes into contact with this webbing is immediately subject to an effect similar to that of a Slow spell.  This effect is fueled directly by the energies of the demiplane of time, and a Chronomancer Wizard's acquired ability to ignore time-magic effects such as Slow is of no benefit against it.  The effect lasts as long as the victim is within the web, or for the standard duration of a Slow spell after exiting the web's area of effect.
• Any Timeweaver Spiders that are in direct contact with the webbing of the lair and remain unmoving are partially engulfed in a slowly swirling cloud of mist-smoke as it flows around the webbing.  They are effectively invisible, and gain Advantage to any attempt to surprise unaware intruders.
• The Timeweaver Spiders within a lair are instantly aware of any arrival or general movement of objects or creatures also inside their lair, even without line of sight.  As an action, any spider may locate any object or creature within the lair.

If all the Timeweaver Spiders in one lair die or leave, any webbing, now no longer maintained, breaks down and disintegrates over the course of 1d4 days.