When Dehaka’s units evolve by munching on each other, there is a chance to mutate if you have put mastery points into Gene Mutation. To show that a evolved unit has mutated, a red glow emits from the unit. Loading mutated units into a nydus worm (specifically done with a Kerrigan nydus, might be the same for other nydus types) will leave their red glow at the location they entered the nydus worm, however reappears back on the unit after the unit is unloaded. Does not change gameplay, and I believe that the mutation still stays with the unit. Bugs are bugs though.
They have a chance to mutate when you reach level 15. Putting points on mastery just adds a higher chance for that.
There is another bug that Creeper Hosts won’t target Air units that only has Ground attacks.
Previously Creeper Hosts target any air units…
Also Tyrant Aura do not affect Pack Leaders