A murder of crows.
A pride of lions.
A coven of witches.
Having originated in hunting terminology, such nomina collectivitatis are known technically as “venereal terms.”
So what's the venereal term for a group of warlocks?
The Warlocks of the Driftless have bruited a number of possibilities.
Dark: a clot of warlocks. (Warlock-magic not infrequently involves blood.)
Eerie: a quantum of warlocks.
Erotic: a tumescence of warlocks. (Warlockry being quintessentially men's magic.)
While it never hurts to consider new possibilities, in fact (as so often), Received Tradition provides an answer to the question: a coven of warlocks.
As with the phrase a coven of witches, a coven of warlocks uses the word coven not in its technical modern (!) sense of “a small group of specific witches/warlocks who meet regularly for worship and magic-making,” but in its older, more general sense of “a collectivity.”
This, of course, makes good sense.
For we are the male of the species, the Witch-Men, and together we constitute covens.