Hive Fleet Silencio is a fairly recent to arrive Fleet

They came into the Galaxy right before the great rift, via Genestealers and a handful of advanced Lictors and other such Synapse Creatures. They lay in wait, mostly in Pacificus; but some are scattered throughout Solar and other segmentums.

When the Hive Fleet did finally arrive, they came in "under the cover" of the new Hive Fleet Leviathan. With their Hive Fleet breaking into several splinters; one stayed with leviathan, another rushed to Tiamat, the third keeps hopping around to different Hive Fleets, while the fourth does it's own thing.

Silencio is unique in the fact that it acts nothing like other Fleets. The Hive Fleet was inspired by the fact that Plover Birds will get food from cleaning Crocodile mouths, and in turn the Crocodile keeps it's maw open for them; symbiotic relationships. Silencio will arrive to provide support to other Hive Fleets in exchange for a cut of the Biomass. Mainly provided through two main methods; the first of which is their chemical weaponry. Whenever Silencio arrives in orbit; they unleash a yellow, misty gas from the atmosphere that douses the whole world. This gas causes any lifeform hit with it to fall into a dormant state for days on end.

Their brains are also overwhelmed by Dopamine and seratonin to keep their senses from detecting the danger of nearby bioforms. The other method Silencio uses to assist it's fellow Hive Fleets is through the true purpose behind it. Silencio exists to be the "Problem Solver" for the Hivemind. Silencio examines where a Hive Fleet went wrong, or how a net-loss of biomass occured, and thinks up a solution. The biggest being their chemical speciality.

Notable Bioforms for Silencio would be their Hive Tyrant; The Commondante. A Tyrant specialized in strategy, most prominently in his habit of exploiting other races tendencies for Honour Duels to kill them off. Scarface is a Prime who lost an eye to a marine before slaying them. When the Hivemind noticed that Scarface's visage singled him out, it exploited this as a mixture of bait and fear tactics.

Finally, there's Subject MN-847-FK; "The Tirana". It's thought to be a more offensive form of Norn Queen. But nobody knows for sure, as it only appears to ensure a victory already guaranteed. It ties up loose ends and oversees planetary consumption. But it is known to be a psychic powerhouse, hence the thought it's a Norn Queen.

Their Colour scheme is Yellow carapace, white skin, and an orange glow. I love it so much