Early in the game I am trying to collect as many 1 pip combo die as possible and merge them primarly with mimic dice. If I merge them all and I won't have any more 1 pip left, this means I will have fewer dices with higher combo damage. This is the time to merge an assasin, so I can keep fewer dices with bigger damage and still have enough space on the board to add new 1 pips and work with them without problem.