When GtP hucks 4 Polus into the graveyard, it feels like it should create 16 graveyard gems. Right now, it only creates 4 gems.
And when a Polu dies, it just resets graveyard gems counts to 4 - does not create 4 more.
https://i.imgur.com/C1dHo1X.mp4
I really hope this isn’t WAD. The mechanic is already underpowered.
Unfortunately that is working as designed. Graveyard gems work like adapt, each card can only create up to the number on the card. (it was mentioned by Support somewhere here, but I can’t find the thread)
I agree that is stupidly underpowered, but that’s the way it is.
Alrighty, then… Done with those cards, I suppose. 
Update: Found the link:
https://forums.505go.com/discussion/81605/titanomachy-and-graveyard-gems-on-bottom-node#latest
@Oktagon_Support said: “It’s important to remember that the graveyard gems are created up to a value, so, it’s the same as if you have sent 5 Chainweb Aracnir (the card that you have used as an example) to the graveyard, the number of graveyard gems on the board will still be 2.”
Thanks and I feel bad for missing that.
So the only way to generate enough Graveyard Gems is to play multiple, different cards with that ability? There are only 10 creatures at Rare and below with this ability - and only 16 if you count all rarities. And those are spread across 3 colors.
Hopefully, they reconsider this implementation one day.
Or by matching as many of the gems as possible before putting another copy in the graveyard.
Either way it makes the mechanic pretty useless, since it would only be good with mass graveyard-dumping stuff that it now does not combo with.
I guess there are a fair number of spells. So the approach is to go all-in on this with an entire deck built largely around Graveyard Gem-making cards.
I guess this is a casual mechanic and nothing more.