Displacer Kitten + Guile + Draining Whelk

Displacer Kitten

Guile

Draining Whelk

How it works

1. Cast any noncreature spell from your hand by paying its mana cost, or wait for an opponent to cast one.
2. Holding priority, cast Draining Whelk by paying 4.
3. Draining Whelk enters the battlefield, exiling the spell and causing you to cast the spell from exile without paying its mana cost due to Guile, and putting a number of +1/+1 counters on Draining Whelk equal to the spell's mana value.
4. Displacer Kitten triggers, blinking Draining Whelk.
5. Repeat from step 3.