Upon entering the battlefield, Gisa and Geralf mill four cards and this can help you put some of your Zombie creature cards into your graveyard for them to later cast from your graveyard once per turn
Its a cool card, but its quite pricey, and is only at its best with five-color tribes like Dragons and Elementals
The same is also true of any other abilities that modify how a land enters the battlefield or apply "as" a land enters the battlefield, such as the first ability of Cavern of Souls

If Chaos Orb flips over completely during the flip, and lands resting on the permanent chosen, destroy that permanent, and then destroy Chaos Orb." - Upon mutual agreement before a match, errata can instead read: "Pay 1, Tap: Destroy target permanent, and then destroy Chaos Orb." Banned List: - Contract from Below - Darkpact - Demonic Attorney Restricted Cards Power Group (Pick 1): - Ancestral Recall - Balance - Braingeyser - Chaos Orb - Mind Twist - Time Walk - Timetwister - Wheel of Fortune Fast Mana (Pick 3): - Black Lotus - Sol Ring - Mana Vault - Mox Emerald - Mox Jet - Mox Pearl - Mox Ruby - Mox Sapphire Restricted List (1 of Each): - Channel - Control Magic - Demonic Tutor - Earthquake - Icy Manipulator - Jade Statue - Regrowth - Time Vault Moderated List (Max of three each) - Berserk - Birds of Paradise - Black Vise - Copper Tablet - Counterspell - Hypnotic Specter - Juggernaut - Lightning Bolt - Lord of Atlantis - Psionic Blast - Savannah Lions - Sedge Troll - Sinkhole - Swords to Plowshares

"1st Official Pokemon Card Game Tournament"