Since its reveal, I've seen numerous comments about how Mamunna is overpowered due to its potential interaction with Griffins. It would make Mamunna a 20 point play for 10 provisions and some people see big numbers like this and immediately scream "OP".
I feel the need to point out that for exactly half those numbers, we find the humble Ghoul. At 5 provisions it is a 10 point play when consuming said Griffin. Requires the same set up (Griffin in graveyard) and is vulnerable to the same tall punishes and resets that Mamunna will fall to.
The difference: Being a bronze we can have 2 Ghouls and only 1 Mamunna (don't mention Caranthir – he's got better targets than this). Also, being an expensive gold, Mamunna grants us the luxury of thinning one card from deck, providing the bronze copy is actually still in your deck.
So Mamunna is just a two-times as expensive Ghoul, with the added benefit of a one card thin. And let's face it – no one has ever had any beef with Ghouls, so why should Mamunna cause any upset
TLDR – New card Mamunna can be a 20 for 10. But the Ghoul is exactly half that value at 10 for 5.