Interesting idea.
May I suggest a rewording of the card text?
Unupped:
"No cards may be played until this card is destroyed. Randomly destroys 1 permanent per turn."
Upped:
"No cards may be played until this card is destroyed. Randomly destroys 2 permanents per turn."
Question: Does it destroy something at the end of the turn it is first played?
If it does, then you might spend 7
for no benefit. I guess that is fair, but I am just wondering if it has "summoning sickness" or not.
The silent forest brings me back to my hometown where I often found myself out in the serenity of the woods. I love the picture too. Maybe someone can make a some similar card art that is not a photo.
As for the effect, I think your new version is relatively well balanced. The high cost means that it isn't likely to be put out quickly and if the opponent has few permanents, you probably won't benefit from this card.
This would be lovely against Rainbow the False God. Rainbow has many permanents and destroying his hourglasses while stopping him from drawing would be amazing.
At the same time, this card probably wouldn't be that clutch in PVP. Most people bring only a few permanents besides pillars and there are lots of rainbow supernova rushes running around that can kill you long before you play Silent Forest.
Overall I can see both how this card would be very useful at times and not that useful at others, but I like the idea.