Also, why a Chaos Seed? Why not make it some other great
new concept? There are more things in
than random effects and mutation, yet that is the main point of 99% of
card suggestions, and it gets boring.
If not, how about randomly place them on both sides of the field on any location, then, when a creature is played there, it gains Chaos Power or Improved Mutation (on your side) or Chaos Seed (on the opponent's side). It would have a set number of traps and the location limited to the next X creature spots past the pre-existing ones.
I think that the caster should be able to see them.
I made this in about ten seconds, is this what you were thinking of (except more Chaos Traps, obviously)?
Or would it randomly choose creatures, mark them, and then use Chaos Seed on them on their next attack?