NOTE | Phasing out is a term I coined in order to describe the physical state that allows a demon to pass through materials, such as solid rock. When phased out, a demon becomes nearly invisible.The ability to pass through material is very beneficial for sucker demons, which prefer to reside in bedding and clothing, which is where they find exposed skin in order to attach to you.
When attached, a sucker demon will usually drain blood or break down muscle tissue; however, they can also incapacitate you in the same manner as acupuncture. A sucker demon accomplishes this by forming a needle at its end, and then penetrating the skin while phased out; then, it punctures a nerve under the skin by phasing back in—amazingly, only at the tip; the rest of its body remains phased out.
When they do this, it's only as painful as acupuncture (which is negligible), but, when applied to the right nerve, can cause total—but temporary paralysis—and loss of sensation in the limb in which the nerve resides. They also use their form of acupuncture to cause tiredness that identifies with any other cause but the true one.
NOTE | Leeches also excrete a mild analgesic in order to mask their presence when sucking blood from a victim.In fact, the only time I ever felt pain from a sucker demon—besides when they intended to cause it, such as when they've shocked me or when back pain comes in handy for an "angry" Voices demon—is when I recognize that one of them is attached and pull it out (and off). But, even that is no worse than the pain of pulling out a hair somewhere on your body.
The fact that it is easy to pull off (and out) a sucker demon suggests that partial phasing is a delicate operation, and is easily disturbed. That may explain why the two sucker demons who entered a hand and a foot, and then proceeded to somewhere in my chest cavity, didn't do so without causing pain. This suggests that when they have to move fast, their ability to phase out is limited somewhat. This is further supported by the fact that you can easily catch a sucker demon that has entered your sheets or clothing, whereas, otherwise, you will never catch one.