If your tenth permanent enters the battlefield and then a permanent leaves the battlefield immediately afterwards (most likely due to the "legend rule" or due to being a creature with 0 toughness), you get the city's blessing before it leaves the battlefield
Plus, theres a high likelihood of zombie players packing some powerful recursion, so even if Gisa does get taken out, it wont be for long
Mind's Desire was so broken, in fact, that it was banned just six days after it was printed, making it the fastest banning in the game's history at the time
The downside, of course, is getting Kaalia to attack safely, but with cards like Anger in your graveyard or by equipping it with Lightning Greaves, you can bypass this hurdle and start flooding the board with oversized creatures like Iona, Shield of Emeria or Griselbrand (or, you know, cards that aren't banned in Commander)