Xiphaem Circuits

Xiphaem circuits, essentially arcane implements within a human body, can accumulate around regular sources of manipulation, generating within the healing flesh. This allows for more control/efficiency with repeated uses of the same general effect. It does not occur when manipulating external blood not from one's own body, such as the Eideli method of xiphaem use, though it can affect the initial outward projection of blood. This limitation is much more lax with ghouls, as it's rather unclear where a ghoul's body ends and 'external' manipulation begins in the first place. In fact, ghouls are more or less giant masses of xiphaem circuits. In the traditional ghoul saying of 'blood, bones, flesh, and nerves', 'nerves' actually refers to xiphaem circuits moreso than any part of a standard nervous system. While said circuits generally utilize electrical impulses, one would be hard pressed to truly compare them to mundane human nerves.
Xiphaem circuits can be implanted into others, though they are generally rejected by the body unless coming from a close relative. Ghouls don't experience the rejection issue, but are instead affected by MSI dissonance when incorporating new circuits- this is often enough to push the ghoul below its sanity point; should the ghoul return, it'll be changed by the experience. Note that this only applies to ghouls explicitly trying to subsume the circuit- eating it normally just breaks the circuit down into its constituent elements and incorporates the material into the ghoul without giving it abilities or causing dissonance.

Common Examples

Whip/flail-like projections

Flexible and hardened portion. Variations include differing length, style of head, mass distribution. Flexible portion can generally be manipulated by application of will.

Projectile

Waves, beams, streams, bursts. All manner of blood-based projectiles.

Armor

Amorphous plating is the most common- essentially a non-newtonian fluid held in place in front of the circuit. Variations on size etc. exist.
There's an entire subcategory of 'skin' armor which essentially maintains a layer of xiphaem at a fixed distance away from one's skin, neatly conforming to movement. Sort of like a glow filter/outline/masking effect.

Reinforcement

Simply a more efficient, easier, and safer reinforcement cast built up due to habitual usage.