Lagrella, the Magpie | Karmic Guide | Preston, the Vanisher

(and one other card)

Cast
Ephemerate by paying ({W} magic symbol) , blinking
Lagrella.
When
Lagrella enters the battlefield, it and
Preston triggers.
Resolve the
Lagrella trigger, exiling
Karmic Guide until
Lagrella leaves the battlefield.
Resolve the
Preston trigger, creating a token copy of
Lagrella that is a 0/1 Illusion.
Put the nontoken
Lagrella into your graveyard due to the legend rule.
If
Lagrella is your commander, choose not to return it to the command zone from your graveyard.
When
Lagrella leaves the battlefield,
Karmic Guide is returned to the battlefield from exile.
Karmic Guide,
Lagrella and
Preston each trigger.
Resolve the
Preston trigger, creating a token copy of
Karmic Guide that is a 0/1 Illusion.
When the
Karmic Guide token enters the battlefield, it triggers, choosing to return nothing to the battlefield.
Resolve the
Lagrella trigger, putting two +1/+1 counters on the nontoken
Karmic Guide.
Resolve the
Karmic Guide trigger from step 8, returning
Lagrella from your graveyard to the battlefield.
Repeat from step 2.