Transfiguration: Charms with the Transfiguration keyword fundamentally change a Colossus’s body structure, far more so than any combination of transhuman implants ever could. The Charm itself is literally a new body which the Colossus’s core can be transferred into, and as such only one Transfiguration Charm may be installed by an Alchemical at a time.
In practical terms, a Colossus should always have a Transfiguration Charm installed unless he is in the vats or in some comparable circumstances where he can do without – or has been deprived of – access to a body. Without one the Alchemical is reduced to a capsule-like core of machinery, unable to move, install Charms, and sense or interact with his environment, though he may still employ Protocols if he is able.
Beyond these basic considerations, the transformation into a hulking construct has a variety of mechanical effects on a character. Sheer size makes it difficult to hide, and to use equipment sized for humans, inflicting a -4 external penalty on such activities without the use of a charm or magical effect to resolve the issue. Worn equipment cannot be used at all unless it is designed for a being of the Colossus’s approximate size and shape.
Such a form is also notably inhuman, making it more difficult to interact with others on a social basis, which reduces the character’s effective appearance by half for purposes of determining appearance modifiers in social combat. More insidiously, this also devalues human interaction, inflicting a -2 external penalty on Compassion rolls to reduce temporary Clarity.
It is not without its benefits however. All transfigured characters ignore penalties for using large weapons up to and including warstrider weapons (Wonders of the Lost Age, Page 150), and those with Essence 7 may also use weapons designed to be mounted on buildings. Additionally, in mass combat they can act as special characters or a unit unto themselves.