Activate Phyrexian Devourer by exiling the top card of your library.
Repeat step 1 until you have an empty library.
Resolve the first Phyrexian Devourer ability, putting a number of +1/+1 counters on it.
If Phyrexian Devourer's power is at least seven, it triggers, causing you to sacrifice it.
Repeat from step 3 for each remaining trigger.
Cast Beacon of Tomorrows by paying ({6} magic symbol) ({U} magic symbol) ({U} magic symbol) , causing you to take an extra turn after this one and shuffle it into your library.
Move to your next turn, drawing Beacon of Tomorrows from your library.