Mausoleum exhaust your opponent's resources
The Mausoleum effect is so strong, because it burdens your opponent with the task of keeping the graveyard empty. Or at least, your opponent has to think twice before he sends powerful military cards or science cards to the graveyard, because you threaten to win with science or military by taking these cards from the graveyard later in the game.
Thus, merely the threat of your Mausoleum forces your opponent to buy many expensive cards, to prevent that you can obtain these expensive cards for free. This places a heavy economic burden on your opponent.
When is Mausoleum not effective?
However, in some games your opponent has such a strong economy, consisting of many resources card and commercial cards, that he can manage to keep all expensive cards out the graveyard without any major expense. And if your own economy is strong too, the Mausoleum effect will be very underwhelming, because your opponent and you will simply buy all the powerful cards and there won’t be any cards to bring back from the graveyard.
To prevent that the graveyard remains empty, you must thus make sure that your and your opponent’s economies are weak. The weaker your economies, the more cards you will both send to the graveyard, and thus the stronger your Mausoleum effect will be.
Setting up for succes with Mausoleum
Making sure that your opponent and you have weak economies is actually quite easy in 7 Wonders Duel. Players are often faced with the choice to make both players better off, or both players worse off.
For example, if you primarily need wood for your wonders and your opponent needs primarily stone, and you can choose between taking a wood resource card or a stone resource card, what do you do? If you have the Mausoleum, you leave the wood for your opponent and you take the stone! This way, your opponent and you will both need more money to build your wonders, and thus you will have less money available to buy other cards, Thus, you must send more cards to the graveyard, and this charges your Mausoleum effect.
These choices between making both players better off or making both players worse off occur all the time in 7Wonders Duel. If you have a papyrus and your opponent a glass, and you get to choose between a papyrus and a glass, you can take the papyrus and leave the glass for your opponent to make both players worse off. You typically won’t need more than one of these kinds of resources, thus both players benefit very little from their extra resource. Whereas, if you would have taken the glass an let the papyrus for your opponent, both players would benefit a lot from their resource. Generally, if both players monopolize one resource, they need to spend a lot more money during the game than if they share the resources equally.
Mausoleum in the Pantheon expansion
The Pantheon expansion makes Mausoleum stronger in some respects and weaker in others. Pantheon generally buffs science based strategies, which the Mausoleum can play a strong roll in. But, the Greek God Hades can retrieve a card from the graveyard as well. Your opponent can use Hades to take a card from the graveyard that you were threatening to take, thus nullifying your threat.
Of course, you can play around this by placing Hades more adjacent to yourself so that Hades is much cheaper for you than for your opponent. This effectively doubles your Mausoleum threat, as you’re likely to revive two cards during the game. This is especially impactful because your opponent generally won’t feel safe anymore to discard two cards with the same science token.
The Egyptians Gods also have a massive effect on the Mausoleum. Players can use Ra to steal a wonder from their opponent if it isn’t built yet. This limits the Mausoleum’s power because a player can’t always wait until the endgame to use it, which is when the graveyard contains the strongest cards. But, players can also use Anubis to build the same wonder twice, which increases the potential power of of the Mausoleum, or use Isis to build a wonder for free, which is especially strong on the Mausoleum because it’s the most expensive wonder.
Pantheon creates balance between science, military and civic win conditions and its Gods introduce many more decision points. For most cards this doesn’t change their power level, but it does make it more challenging to play them optimally. The same is true for the Mausoleum, as players need to think about the effects of Hades, Ra, Anubis and the other Gods on their game plan.