Hoarding Broodlord + Nexus of Fate + Soulherder

Steps

1. At the beginning of your end step, Soulherder's second ability triggers, blinking Hoarding Broodlord.
2. When Hoarding Broodlord enters the battlefield, it and Soulherder's first ability trigger.
3. Resolve the Soulherder trigger, putting a +1/+1 counter on it.
4. Resolve the Hoarding Broodlord trigger, searching your library for Nexus of Fate if it's in your library, and exiling it.
5. Cast Nexus of Fate either from your hand or from exile by paying {5}{U}{U}, causing you to take an extra turn after this one and shuffle Nexus of Fate into your library.
6. Repeat each turn.