Enchant creature
As long as enchanted creature is green, it gets +1/+1 and has indestructible. (Damage and effects that say "destroy" don't destroy it. If its toughness is 0 or less, it still dies.)
As long as enchanted creature is white, it gets +1/+1 and has flying.
(01/05/2008)
If an effect would simultaneously destroy Shield of the Oversoul and a green creature it’s enchanting, only the Shield is destroyed.
(01/05/2008)
If the enchanted creature is both of the listed colors, it will get both bonuses.
(01/07/2013)
If a green creature enchanted by Shield of the Oversoul is dealt lethal damage, the creature isn’t destroyed, but the damage remains on the creature. If Shield of the Oversoul stops enchanting that creature later in the turn, the creature will lose indestructible and will be destroyed.
