Depending on the number of players and the Myrrh cycle, a creature's HP will be boosted by a multiplier, as follows:

1 player 2 players 3 players 4 players
Cycle 1 x1.25 x1.50 x1.75
Cycle 2 x1.50 x1.875 x2.25 x2.625
Cycle 3 x2.50 x3.125 x3.75 x4.375