The Mummy paradox of which you talk tells you that that card could be unbalanced.
Mummy costs 4
![Death :death](https://elementscommunity.org/forum/Smileys/solosmileys/../../../images/Misc/death18x18.png)
and is a 5/3 creature + an ability with a duo requirement. So that adds
4
![Death :death](https://elementscommunity.org/forum/Smileys/solosmileys/../../../images/Misc/death18x18.png)
= 5(attack) + 0(HP=3) + 1(Ability) - 1 (Requirement) - 1(Duo)
![Shocked :o](https://elementscommunity.org/forum/Smileys/solosmileys/shocked.gif)
This seems to be a hole in the calculations. If we gave Abomination, or any other vanilla creature, an ability with a duo requirement its cost lowers by 1.
LOL
![Laugh :))](https://elementscommunity.org/forum/Smileys/solosmileys/laugh.gif)
I didn't notice that. NICE
OH! and upgraded versions seems to always cost -1 or -2 of what they should cost.