Should several players be trying to simultaneously conquer a castle, the player with the highest silver ratio (silver sent / silver needed) will successfully conquer the habitat. 

For instance: 

Player A will need a 1.000 silver and sends an additional 1.000 silver (so 2.000 in total) which makes a ratio of 2 or 200%.

Player B only sends the required 5.000 silver which he needs, possessing 5 castles.

In this case player A will conquer the castle.

Player B would require 10.001 silver to conquer the castle in order to beat the silver ratio of player A in this example.

If both players send the same ratio of silver, the player who conquers the castle is decided at random.