This alone makes it a powerful card, but if you activate the second ability on Academy Ruins, on your upkeep to put Mindslaver back on the top of your library, then you draw it on your turn, repeat the process, and play the game alone
Being able to sacrifice the big creature you Stationed it with to get a massive hand refill is very, very efficient for just three effective mana and two life
Some of the creatures have the new squad keyword, which basically works the same as replicate (see Train of Thought) only for creatures, giving you tons of built-in ways to multiply your creatures with ease
As a flying, lifelink 3/5, it rewards gaining and losing life by handing out +1/+1 counters or reanimating creatures from your graveyard
Dhelmise #10Common $0.08 Gouging Fire #38Rare $0.18 Exeggutor #3Uncommon $0.04 Feebas - 041/191 #41Common $0.07 Fuecoco #29Common $0.10 Morelull #8Common $0.07 Exeggcute - 001/191 #1Common $0.14 Cryogonal #47Common $0.06 Capsakid #12Common $0.03 Larvesta - 024/191 #24Common $0.06 Ceruledge #98Rare $0.25 Ceruledge #20Uncommon $0.13 Ceruledge #70Common $0.16 Ceruledge #31Rare $0.64 Ceruledge - 014 #14Promo $12.70 Ceruledge - 014 [Staff] #14Promo $92.35 Ceruledge - 022/106 #22Uncommon $0.12 Ceruledge - 040/091 #40Rare $0.16 Ceruledge - 091/190 #91None $0.20
Source (includes a link to the exhibition page with full details)