It was rather disappointing, but maybe he could do something with the raw warp stuff at some later point? There were a lot of new opportunities open to him now, after all, and it would take time to explore them all.
Making a familiar would be neat, for when the psyker goes mask off or if Tide finds a way to make the thing look both holy and be only visible to psykers as tutelaries are. Or just make it look like a psyber familiar and pretend the Genetor made it (I think by the latest posted chapter he's already infected?) for her.
Why is a familiar useful? They let a psyker null miscasts. Straight up. The only downside is that nulling a miscast sometimes results in there not being enough power to make the power happen.
This is based off of Warhammer Fantasy Roleplay 2e, but it's canon that warp shit stays the same across both 40k and Fantasy.
Also, fun fact, there's a tier of daemon below lesser. Least. That's where Furies are and also the little-known imps.
Imps are the least of the least, minor Daemons that are born from loosed
emotions. In their "natural" state, they are amorphous things, endlessly
cycling through a variety of shapes that seem to reflect the thought or
concept that birthed them. It is only when a Dark God claims an Imp
that it becomes something. Dark Magisters and Chaos Sorcerers conjure
Imps to serve as Familiars.
Bubo
Imps of Nurgle are tiny versions of Nurglings, being delicate, fragile,
foul, and green. They look like small withered peas but are dimpled
with sphincters that issue foul yellow wetness. These creatures thrive on
sickness.
Fearling
Imps of Tzeentch are small balls of pink flesh, like a miniature Horror
of Tzeentch. It sits and quivers, expelling blue and pink flames from its
many mouths. When it moves, it pulls itself along with pseudopodia,
scorching the ground wherever it goes. Fearlings inspire rebellious
thoughts and acts of anarchy.
Malice
Imps of Khorne are miniature warriors encased in black armour. They
look like tiny Chaos Warriors and indeed, they have the temperament
of the most vicious Khorne Champion. Malices feed on rage and hate,
inspiring both in mortals.
Muse
Imps of Slaanesh are appealing, taking the form of beautiful young
women with perfect nubile bodies and long hair of scintillating colours.
They are tiny, no taller than three feet, but despite their size, they have
power over men, stealing their souls, and draining away the capacity for
sensation. But they are also inspiring, urging their victims to new heights,
always pushing further and further to attain the glory they seek.