I guess mill support like Foolish Burial and the Ishizu EARTH/Fairies can get Slifer in the GY easily, but then it's a matter of drawing this and then waiting for a direct attack, and even then, nowadays most modern decks have ways to deal with 3000+ ATK beaters without any sort of protection, although admittedly I do have seen duels where decks do not have outs to such cards or have already spent their resources.
The rest ramp, card advantage, and the colorless staples every EDH deck wants
However, by the end, I was quite amused by the narrative it presented
During your Main Phase, except the turn this card was sent to the GY: You can banish this card from your GY, then target 1 "Drytron" monster you control
This card is a powerhouse thats already overpowered and is even stronger when it triggers twice
Elemental Teachings hits some of the same notes, but is way less effective at 5 mana