Each upkeep? That's awesome, but probably too powerful.

Well, um, it costs 9. It has the same casting cost as Myojin of Life's Web. I'd compare it to something else that costs 9, but, you know, besides Artisan of Kozilek, there hasn't been anything else competitive that you can cast with 9 Forests. At 8, though, is Liege of the Tangle, which hits once, and immediately gives you an army of 8 8/8s.

Though, I will admit, that often when we get to this level, there's some sort of anti-Zombify clause. Both the Myojin and the Artisan have one...

Oh yeah, reanimating this into existence would be pretty horrific.

I think the level of stompy is about right; but it probably does want to at least partly avoid that. After all, it's still 9/9 trample when reanimated,

As far as I'm concerned, if a card costs about 7, then it's a fair reanimation target, since you're only shaving 3 mana off in the process. When a card starts to push into the 9+ range, though, the casting cost becomes meaningless unless some sort of "can't cheat this into play. You must cast me correctly" clause isn't invoked. Darksteel Colossus shouldn't be cheated (though, I know people like to Tinker him... let's not go there). You should have to pay for it. That's what lets it be so awesome.

Removed giving other beasts trample and added an "anti-reanimator" clause.
flavour text which wouldn't fit is "This most ancient of all Baloths is surprisingly elusive for its size."

­Verdant Force but 3/3s instead of 1/1s? Yowsers. Verdant Force (and its cousin Mycoloth) are still very popular at casual tables.

Heh yep, have fond memories of Verdant Force, changed this down to a 6/6 so it wasn't quite so nasty.
I personally think that the anti-reanimator makes up for the size diff in the tokens to a large degree, and dropping it to a 6/6 makes it less awesome in its own right.

The other option was leave it at 9/9 and only make the tokens on your upkeep.

You could make all the tokens during your upkeep. "put a number of 3/3 green elemental creature tokens into play equal to the number of players." The end result would be the same if someone wasn't able to answer it, but it would give people time to come up with a proper answer.

Personally, though, I think 9cc card should be crazier, though, not reserved. I mention it as an option, not as my preference.