Questions about a couple Illusion skills

Hi, I just want to make sure I understand how a few things work.

One, Fragility. It triggers whenever the target gains or loses a condition. Does Knockdown count as a condition for this purpose?

Similarly, can Knockdown be spread by Epidemic?

Finally, Arcane Echo. When it replaces itself with another skill, does it change completely, or does it still have the casting time and recharge time of Arcane Echo itself? I thought I might have read somewhere that it works that way.

Knockdown is not a condition.

Arcane echo will gain the skills energy cost and recharge time. Its exactly like having the copied skill on your skill bar, just temporarily though.

The first is kind of a pity, but not unexpected. The second I'm glad of, as it makes Trident spamming easier.

Thanks so much!

Also, Fragility does not count on a "refresh" of a condition. For instance, if the foe is already poisoned and you hit them with poison, it refreshes the timer, but does not trigger the Fragility damage. This is because the opponent never "recovers" from the condition.