This character can split apart into two or more pieces, with the parts being able to function independently. The character can split off one piece as a simple action. The detached piece will have a half action to spend this round after detaching, and act normally on the character's initiative thereafter.
The character may split into a maximum number of parts equal to his rank in this power minus one, meaning that you need at least three ranks to actually use it.
For every full three ranks in Split, the smallest splittable piece is one size class smaller than the base character. If you wish to be able to split off smaller pieces than this, buy Shrinking with the Flaw "Only usable by split-off pieces". The total effective ranks in Shrinking cannot exceed the character's PL, however. The use of buying separate shrinking is to let characters only be able to detach one or two small pieces. At the player's option, the remaining "core" of the body may also reduce in size once the maximum number of splits has happened.
Split pieces default to having all powers and abilities of the base character (with powers limited to a number of ranks equal to the ranks in Split), and are affected normally by loss in size class. If not equipped for movement, they will be able to hop or roll at the relevant running speed. It's probably a good idea to have Flight, at least with the Flaw "Only usable by Split pieces".
Pieces may reattach as a free action if they are within 5' of any other piece. Damage to pieces is resolved as per the power Duplication, but they are automatically considered to be permanently lost if destroyed, and need to be replaced via Regrowth or plot contrivance.
Pieces must stay within Normal range of the core character.
-All Duplication and Shrinking Extras are applicable.
-Defensive Split: Split apart to avoid an attack. Gain a Dodge Bonus equal to ranks in Split.
-Arbitrary Split: The base power assumes you split along pre-determined lines. With this Extra, you can split at any point, then heal back together. This also means that if someone else tries to split you apart, you can heal that damage. Gain Regeneration equal to ranks in Split.
-Range: If the Range extra is taken, the pieces can range farther afield. However, if they get out of sight, the character can only use normal senses associated with the piece.
-Point Of View: The character can use all senses through any piece, even if it lacks the relevant sensory apparatus.
-All Duplication and Shrinking Stunts are applicable.
-Cloud: Only available if 9 or more ranks of Split are bought. Instead of splitting normally, the character may take on Alternate Form: Semi-Solid as a cloud of components.
-Combat Split: A part split from the main body may take up to a full move and then perform a melee attack. Usually this takes the form of flying straight at the opponent.
-Mix And Match: The pieces can recombine in multiple fashions, granting a Shapeshift-like ability. This is usually not as effective as true Shapeshift, unless the character can split into very small pieces.
-Permanent may not be taken on this power.
-Blockable: There is some reasonably obvious way to keep the core (usually the head or head and torso) from controlling the pieces. A few minutes of observing the character in action, plus a DC20 INT check, will let someone deduce this. Pieces blocked off from the core go limp and inert. Common means of blocking control are: forcefields, lead walls, covering the character's eyes, placing glass between the character and the piece (this one was the actual weakness of Captain Marvel).
-The Hard Way: Pieces don't just come off easily, they have to be cut or torn off by the character. Treat this as a lethal attack against the character with a strength equal to the ranks in Split minus the number of sizes smaller than the character the piece is to be (i.e. cutting off a finger doesn't hurt as much as cutting off an arm). This will always do a Hit, but a Hero Point may be spent after a failed save as normal to avoid being Stunned or Disabled. The piece cannot automatically reattach, but if somehow secured (such as by needle and thread) it will function normally.
-Limited Splits: The character can only split into a number of pieces equal to one third (ignore fractions) of his ranks in Split, and the specific pieces must be specified when this power is taken. The purpose of using this instead of buying Shrinking for the pieces as discussed above is to allow each of the pieces to operate at a higher rank.
-Feeble Splits: Each piece can only have one of the character's powers, preferably one that seems to fit (i.e. running for a leg, energy blast or strike for a hand). It is limited to movement that would make sense for it (hopping, crawling, rolling) unless it has Flight. Multiple pieces may have the same power, they are simply limited to one each.
-Range: If the Range Flaw is taken, all pieces must remain in adjacent squares, or within 5' if mapped movement is not used. If taken twice, the power cannot be used at all, congratulations.
A bit complicated to consider for a house rule power, but have fun trying it out in tabletop!