The interesting aspect of this card is that the card draw comes at the beginning of your second main phase
so a 1/3 on defense was actually kind of a stop sign against a legion of 2/1 creatures
Accorder's Shield Bone Saw Cathar's Shield Claws of Gix Darksteel Relic Everflowing Chalice Fountain of Youth Herbal Poultice Intervention Pact Kite Shield Memnite Mishra's Bauble Mox Amber Mox Jasper Mox Opal Ornithopter Pact of Negation Pact of the Titan Paradise Mantle Slaughter Pact Spellbook Spidersilk Net Summoner's Pact Tormod's Crypt Welding Jar Zuran Orb
Put a base toughness 4 counter on target creature The effect of a base power 4 counter or base toughness 4 counter overrides any existing effects that set that creature's base power or toughness, as appropriate
Sentry also brings us to an important topic: What does this deck lose to
Aboshan, Cephalid Emperor Aesi, Tyrant of Gyre Strait Arixmethes, Slumbering Isle Brinelin, the Moon Kraken Caelorna, Coral Tyrant Caetus, Sea Tyrant of Segovia Charix, the Raging Isle Gyruda, Doom of Depths Gyruda, Doom of Depths Kamiz, Obscura Oculus Koma, Cosmos Serpent Koma, Cosmos Serpent Koma, World-Eater Krothuss, Lord of the Deep Llawan, Cephalid Empress Lorthos, the Tidemaker Lorthos, the Tidemaker Marvo, Deep Operative Monstrosity of the Lake Octavia, Living Thesis Queza, Augur of Agonies Shark Shredder, Killer Clone Sin, Spira's Punishment Sin, Unending Cataclysm Slinn Voda, the Rising Deep Taniwha The Terror of Serpent's Pass The Unagi of Kyoshi Island The Watcher in the Water Tromokratis Ultros, Obnoxious Octopus Verazol, the Split Current Wrexial, the Risen Deep Xolatoyac, the Smiling Flood Xyris, the Writhing Storm Yorion, Sky Nomad