I love playing this game and I do overthink things so that's why I am popping up in this forum so much.
I noticed that when a creature dies and spawns a Skeleton, the Skeleton occasionally gets to attack immediately and sometimes it doesn't. The attack sequence that I noticed is based on the "order" of placement. So if a creature attacks and dies (either to poison or fire shield), their Skeleton can attack if it spawns in a later position of attack.
C: creature
E: empty position
Setup : CECCC
Order : 34152
if the creature in position 1 attacks and dies, the skeleton spawns in position 4, the 2 followed by 3 attacks, the skeleton attacks and 5 attacks
Setup : CECCC
Order : 34152
1, 2, 3 and 5 attack, 5 dies and a skeleton spawns in 4 but doesn't attack