I never really got Krystalak from the Godzilla games, was he supposed to be one of the crystal based lifeforms Spacegodzilla was spawned from when the G-Cells were sent into space?
He started life as a Crstal of SG. When that went into the earth, Krystalack abosrbed the energies and became what you see above, It's the same with Obsidous, except he abosrbed Geothermal energy as well.