As is referenced in the flavor text, each of the pokémon in the grid is to be categorized by its type, its number of evolutionary stages, and the generation of games it originated in. Color coding the grid can help patterns emerge. Here are the pokémon sorted by type (Note that all the pokémon used in this puzzle have a single type):
The only types which are adjacent to others of the same type are the normal, psychic, and water pokémon, which make the letters to spell out ICE, another pokémon type.
The number of evolutionary stages grid looks like this:
The one-stage pokémon form a number 1, suggesting that the answer is a single-stage pokémon as well.
Finally, sorting by generation looks like this:
The colors in this one are a bit noisy, but it is still possible to read a G5 in the Gen 1 and Gen 3 blocks.
These results suggest that the answer is an ice type from generation five, with a single evolutionary stage. The only pokémon to match these criteria is CRYOGONAL.