It gets +X/+0, where X is the greatest power among creature cards in your graveyard
Add to that the second most potent card draw engine in Underworld Connections (second only to Jace, Architect of Thought into Sphinxs Revelation) and there are some rich incentives to cast black cards
Great Oak GuardianGreat Oak Guardian is more interesting thanks to flash, but that isn't enough to make it worth keeping

Take a look at the entire Commander deck below: Creatures (30) 1 Sakura-Tribe Elder 1 Forgotten Ancient 1 Ulasht, the Hate Seed 1 Fertilid 1 Taurean Mauler 1 Spearbreaker Behemoth 1 Goblin Razerunners 1 Acidic Slime 1 Champion of Lambholt 1 Genesis Hydra 1 Primeval Protector 1 Rishkar, Peema Renegade 1 Loyal Guardian 1 Whiptongue Hydra 1 Krenko, Tin Street Kingpin 1 Grumgully, the Generous 1 Ox of Agonas 1 Agitator Ant 1 Chishiro, the Shattered Blade 1 Walking Skyscraper 1 Towashi Guide-Bot 1 Orochi Merge-Keeper 1 Tanuki Transplanter 1 Rampant Rejuvenator 1 Kosei, Penitent Warlord 1 Akki Battle Squad 1 Kami of Celebration 1 Komainu Battle Armor 1 Kaima, the Fractured Calm 1 Ascendant Acolyte Lands (37) Spells (33) 1 Sol Ring 1 Rampant Growth 1 Kodama's Reach 1 Decimate 1 Starstorm 1 Fireshrieker 1 Elemental Mastery 1 Soul's Majesty 1 Mage Slayer 1 Chain Reaction 1 Bear Umbra 1 Snake Umbra 1 Sword of Vengeance 1 Bonehoard 1 Beast Within 1 Chaos Warp 1 Hunter's Insight 1 Swiftfoot Boots 1 Ordeal of Nylea 1 Shamanic Revelation 1 Rishkar's Expertise 1 Shifting Shadow 1 Blackblade Reforged 1 Rhythm of the Wild 1 Arcane Signet 1 Vastwood Surge 1 Invigorating Hot Spring 1 Silkguard 1 One with the Kami 1 Collision of Realms 1 Concord with the Kami 1 Smoke Spirits' Aid 1 Unquenchable Fury The deck was accidentally printed with two copies of Mossfire Valley, so players will need to swap a copy out for another basic land or a land of their choice not already in the deck to play it out of the box

What should be in a MTG Commander deck