The energy is an integer number ranging from 1 to 49, which is related to the speed. The relationship between the energy and the speed is described as a monotone increasing function, for instance, 10 energy for speed 10 (+0 speed), 20 energy for speed 20 (+10 speed, 'Fast(+10)'), 30 energy for speed 30 (+20 speed, 'Fast(+20)'), 38 energy for speed 40 (+30 speed, 'Fast(+30)'), and 42 energy for speed 50 (+40 speed, 'Fast(+40)').
A normal action take a random energy whose average is 100. This is normal distribution with standard deviation 31.
As for the speed of monsters, you should notice that not all monsters are created equally. If the monster is neither unique nor in the Arena, it will be created with a speed ranging from 2/3 to 4/3 of its base speed. For instance, a Power Wyrm can be created with a speed ranging from 20 to 40, i.e. +10 to +30 speed, as its base speed is 30. The possibility of creating a monster whose speed is far different from the base speed is low, but it is still possible. This matter is important especially for a player who usually rides on a monster. The speed of a monster also affects the amount of experience a player can be awarded by killing that monster. Faster monsters award more experience to a player.