+1 to one creature per turn is not really going to help much.
And if you have multiple ones on the field, it costs too much.
I disagree. Most dragons have around 5 health, so one shot of this coupled with Gravity Shield is enough to stop them cold.
Combine that with a continuous source of Otyugh health and this could be scary - Otyughs will be able to gain 2 health per turn instead of 1.
Gravity also does not have a shield that deals with creature damage. Use Gravity Shield and you can catch the larger critters with this, and neutralize the attack of the lower ones. Dropping your opponent's attack by one each turn is more powerful than it sounds, consider the fact that Arsenic by itself can wreak havoc eventually but it's only
adding one damage per turn.
I can imagine a somewhat scary earth-gravity deck involving a Pulverizer, PA/Gravity Shield, this little guy, and a couple Otyughs. Maybe toss in a few Chargers so your damage doesn't rely as much on opposing creatures.