After seeing the deck posted by uppercut, I agree that this is slightly OP. There are two fixes to this, both are easily done:
1. Make the 6 card limit apply (if it doesn't already apply, I wasn't quite sure if it does or doesn't)
2. Increase the cost to 5 unupped, 4 upped. This does weaken the card slightly, but it would still see a ton of use. I, for example, would run a few gravity ones in my scarab charge.
Either of those will do the job. Honestly, I would go with the first, seeing as this card SHOULD be affected by the 6 card limit seeing as is it not a pillar/tower/pendulum.