The matchmaking algorithm is the unsung hero that determines exactly who you will face every time you press the 'Battle' button.

While this conspiracy theory is widespread, the reality is much more mundane and focused entirely on mathematical fairness.
Trophy and Rating Systems
Your trophy count is a numerical representation of your skill; win a match, and you take trophies from the loser.

When you go on a massive winning streak, your trophy count inflates, and the algorithm begins matching you against significantly better players.
The algorithm does not care what deck you are playing.With millions of players, you will occasionally draw a bad matchup.In the lower arenas, the system often includes 'bots'. Level-Based Matchmaking
The standard Elo system works perfectly for chess because all pieces are equal, but tower rush games feature upgradeable cards.

To combat this, developers have implemented secondary checks that look at the player's King Tower level.
Matchmaking FactorSignificanceElo RatingAbsolute Highest PriorityAccount StrengthSecondary Priority Maintaining Competitive Integrity
Because the ladder algorithm must balance queue times against fairness, it will never be perfectly balanced.

The algorithm is blind; it only respects victory.