I remember seeing several discussions on rare cards.
A couple points I saw come up, that I thought would be relevant here:
1) Rare cards need to be balanced. This is actually MORE important for rares than non-rares.
---There are several reasons for this but the main one is that it will be very frustrating for beginners if rare cards are too powerful.
---This is particularly true now that arena is effectively the main place to gain rares. If rares are too powerful, then only players that have rares to begin with will be able to grind arena decks successfully in order to get more rares... So basically anyone just starting out gets #insert 4 letter word here#ed over.
2) Rare cards should be useful even with just a single copy in a deck.
---Again, needing to have 4 or 5 copies of a card that is hard to get just a single copy of is quite frustating for new players... think of how long it took you to grind for all those shards... now imagine how a beginner is going to feel if they realize that the rare they just grind for several days to get is useless without 3 to 5 more copies.
That said, I think seeing more rares in the game to balance out each of the nine other elements is a great idea.
Going forward with that, however, I think these rares should be obtainable from the level 3 AI's and up... Pharaoh is currently, arctic squid used to be and I think really should be again, as should miracle.
What I would suggest is:
1) Get a vote going to pick candidates for rares to fill out the other 9 elements.
2) Once the rares candidates are selected, have an event / competition /etc. to encourage players to come up with new level3 AI's that include the new rares. (we had a tournament like that in the past... I'll have to dig up the link)
There are already 4 rare-series, so I don't think that there should be more. If there would come another one, that would be fine too.
I agree here, although I think its really more like 4 complete series' (nymph mark weapon shard) and one incomplete 5th series... I think the best option is to flesh out the 5th 'series' (pharaoh, squid, miracle) to include 1 rare for each other element.
Also of note... of the 3 rares in the 5th series, none of them are permanents.