Originally Posted by KaAnor

There is also the friend help in battle that I didn't understand (I haven't really tried ...), but the friend seem to lend a card to the one in battle, if not you will have a low level Airu instead. Don't really know how it works but friends will help once again.

Trying to clean up Google's mess on the HELP section:

PeroColliseum dedicated CENTER UNIT will be called as HELP.
If you leave a high SED card in the CENTER PLACE, it may be able to help your PeroFriend win.
Be specially careful to note this is not center card in My Pero.
There is no reward given for helping, even in a victory.

If you've never played PeroColliseum before, the deck-building window will auomatically open if you try to enter PeroColliseum and you have 5 or more cards.
You don't start participating PeroColliseum until you've personally validated a deck.
(I'll finish this later)