Sandsteppe Mastodon + Stampeding Serow + Sage of Hours

Sandsteppe Mastodon

Stampeding Serow

Sage of Hours

How it works

1. Cast Sandsteppe Mastodon by paying 5.
2. Sandsteppe Mastodon enters the battlefield, putting five +1/+1 counters on Sage of Hours.
3. Activate Sage of Hours by removing all +1/+1 counters from it, causing you to take at least one extra turn after this one.
4. Move to your next turn.
5. At the begging of your upkeep, Stampeding Serow triggers, causing you to return Sandsteppe Mastodon from the battlefield to your hand.
6. Repeat.