THM Astral Fire/Umbral Ice stacking

[DayumQuitPlayin]

Will someone explain in detail how do Astral Fire and Umbral Ice stack?

The Magick and Mend level 20 trait reads: Increases base action damage and HP restoration by 10% and allows for the stacking of a second Astral Fire or Umbral Ice.

Now, I understand that Astral Fire makes your Fire-related attacks stronger and Umbral Ice give you an MP regen, but what I don't understand is the "stacking" part.

Example: When I use Fire I see the Astral Fire buff, when I use Fire again, I see the buff icon has "II" on it. I just don't understand what it does exactly or how to use it.

Does it just mean that it's more potent? Example: Fire attacks are even more stronger and MP regen is even more after "stacking"

Thanks in advance

[Astralis]

Yes. If you can stack up to two times, Astral fire 2, gives more bonus damage to your firespells, but increases their sP cost twice as well, while having Umbra Ice 2, gives you twice the MP regen you have than Umbra Ice 1.

you can see the stack on the buff icon on your screen, as well as a message will pop up beside your character if you get a buff, first fire1 astral fire, 2nd fire 1 astral fire 2

[rzr22]

I'm pretty sure multiple stacks of Fire does NOT increase MP cost past the first stack. I can only test two stacks, but right now with one stack my Fire costs 90 and with two stacks my Fire costs 90.

[Foullacy]

I'm pretty sure multiple stacks of Fire does NOT increase MP cost past the first stack. I can only test two stacks, but right now with one stack my Fire costs 90 and with two stacks my Fire costs 90.

Every stack of Astral Fire increases the mana cost of your Fire spells and decreases the mana cost of your Ice spells. At three stacks of Umbral Ice your fire spells have a drastically reduced cast time and vice versa for Astral Fire.

[rzr22]

Every stack of Astral Fire increases the mana cost of your Fire spells and decreases the mana cost of your Ice spells. At three stacks of Umbral Ice your fire spells have a drastically reduced cast time and vice versa for Astral Fire.

Except it doesn't. Like I said. I was in-game while posting that. Astral Fire I - 90 MP Fire. Astral Fire II - 90 MP Fire. I'll even post a video once I login since people are so incompetent to use their eyes.
EDIT: It's possible this changes at higher levels or when you can stack Astral III. With that being said, at my level, multiple stacks of Astral Fire does not increase the MP cost further.
Here's the video: http://youtu.be/SBy1bv-u0O0

[DayumQuitPlayin]

Ah ok, so it just makes it more potent, I got you.