I used to play with a legendary Shrine deck liberally strewn with Mirror Gallery cards. Didn't have a creature card in the entire deck, which meant it was a little hit and miss, but with 4 of every shrine in the deck it could be potentially invincible. To put that into context; with two of every shrine I could gain 40 life a turn, deal 20 damage to target creature or player (in two lots of 10 damage), play 20 1/1 colorless spirit creatures, cause my opponent to discard 20 cards, and draw 20 cards. Each turn. Wasn't too bad with just one of each either. Was a bit vulnerable to anything that could destroy artifacts, and needed a lot of lands, but it worked well for me.