+1 / +1 Counter: Use for Power and toughness alteration

Blackcleave Cliffs Blood Crypt Blooming Marsh Boseiju, Who Shelters All Botanical Sanctum Bottomless Vault Bountiful Promenade Breeding Pool Cactus Preserve Caldera Lake Canopy Vista Canyon Slough Castle Ardenvale Castle Embereth Castle Garenbrig Castle Locthwain Castle Vantress Cathedral of War Cave of the Frost Dragon Celestial Colonnade Chocobo Camp Choked Estuary Cinder Glade City of Ass Clifftop Retreat Coastal Peak Commercial District Concealed Courtyard Copperline Gorge Cori Mountain Monastery Creeping Tar Pit Crypt of Agadeem Dalkovan Encampment Darkslick Shores Deathcap Glade Den of the Bugbear Deserted Beach Dragonskull Summit Dreamroot Cascade Drowned Catacomb Dungeon Descent Dwarven Hold Eclipsed Steppe Elegant Parlor Emeria, the Sky Ruin Exclusive Nightclub Festering Thicket Fetid Pools Field of the Dead Fire Nation Palace Flamekin Village Foreboding Ruins Fortified Beachhead Fortified Village Frostboil Snarl Furycalm Snarl Game Trail Gilt-Leaf Palace Glacial Fortress Glasspool Shore Glittering Massif

While the second mode is rarely worth using, for three life is hardly worth one additional mana, it's still nice to have the possibility for it to become a board-wide protection spell if you needed it
There was a land that tapped for both colors and a couple cards that let me search for lands, so my mana was pretty good
You stockpile them and they persist across phases and turns until you spend them
Im a huge fan of the Ice Age block, including Coldsnap, so Id have loved to see Dark Depths in this slot