You would take half with Gisela out, so just a single damage per nonbasic land you are running, while your foes double, so essentially four damage per nonbasic land they control
Led by Quintorius, History Chaser, a planeswalker , this deck is built to generate spirit tokens and isn't afraid to let cards head to the graveyard because there are ways to either cast the card again (Flashback) or, in the case of creatures, bring them back to the battlefield
This makes Six an effective way to use your entire graveyard as extra cards in your hand
Imagine cards like Bitterblossom, Jadar, Ghoulcaller of Nephalia, and Ophiomancer just saying create a Treasure every turn or upkeep. Its even an okay card in the face of a board wipe since you get more than enough mana to rebuild afterwards
At least you do have to risk something to get what you want