The black warlock is a butterfly that players can capture with the Hunter skill at level 45 or above, granting 54 Hunter experience.
Capturing a black warlock is a task sometimes assigned by Sherlock during an elite clue scroll.
The hunting technique is the same as for other butterflies. Players must wield a butterfly net and have at least one butterfly jar in their inventory to catch any butterfly. One jar is needed for each butterfly you wish to keep. All of these items are available for purchase in Hunter shops.
One can use a jarred black warlock on another player to increase their Strength by 15% + 4, rounded down. This will only work in multi-combat zones, and only if the player is on your Friends List. This can't be used on ironmen since ironmen can't accept aid from other players.