Hmmm... I have to agree with Chapuz that there is too much poetential for abuse.
More important than aflatoxin, there is the fractal, boneyard, and possibly nightmare abuse issues as well.
The 1 hp helps, to be sure, but I don't think its enough. Plop this guy into a fire-bow and that 1 HP really isn't much of an obstacle. You have momentum, chaos power, blessing, plate armor, and SoPa to work with to overcome that problem.
For that matter, pop this guy into a fractal-photon or fractal-brimstone eater deck and add in a couple immolates and momentums.
Alternatively, do the same with a boneyard deck... add in photon or spark and immolate to get rolling and a handful off buffs.
At the very least if you intend to keep +3|+0 you should stick to only enemy creatures. That would help avoid many of the abuse issues.
If you tone down the bonus to +1|+0, then it might work to keep same side bonuses...
The big problem you will face with same side bonuses, however, is that you have to consider the extreme case of 20+ smaller allies.
In order to balance it for that case, however, you would have to make it so prohibitive that it would end up becoming a forced combo.
This is very much akin to a number of previous card ideas that grow based on other copies in play and the balancing issue is essentially the same... If you balance it to be okay with a large number of allies then it will end up being UP unless used in a forced combo. If you balance it to be useful in more generic low creature count situations it will become very OP in high creature count situations. Kind of a catch22.
As an alterntative, you could restrict it to only benefit from weaker creatures in the same field row. In that case, you only have to balance against 7 creature at maximum and about 1 to 3 creatures on average. This is much more doable.
