The Slipskull is a fast enemy, and have the advantage of clinging to walls. This makes the Slipskull a difficult target to hit. Their speedy and stealthy forms make them excellent scouts as well as ambushers. Once detected, it is necessary to eliminate these creatures as soon as possible before they summon reinforcements.
Slipskulls are easily detected by the sounds they make as they jump. While preparing to fire they will shine a laser sight from their Reaper Carbine which also assists in locating their location.
To combat the Slipskull's speed, use the L23 Fareye's secondary fire which is ideal in taking them down.
Slipskulls can only jump to scripted positions in any given room, and will alternate between these positions. Simply aiming at one position while taking cover from the others allows the player to defeat any number of Slipskulls with a little patience.
Their own weapons, the Reaper Carbines, unlocked on the second playthrough, is also useful in tracking a Slipskull's movement.
Using the Fareye FR-1's secondary mode will help to slow the slipskulls motion down before using the primary fire to kill them, but it also get a Skill Points for killing all Slipskulls in Paris Catacombs.