Hatchery Sliver + Maskwood Nexus + Shield Sphere

Hatchery Sliver

Maskwood Nexus

Shield Sphere

How it works

1. Cast Shield Sphere by paying 0, and choosing to pay its replicate cost an arbitrarily large number of times by paying 0.
2. Shield Sphere triggers, creating a copy of it for each time its replicate cost was paid.
3. Resolve all Shield Sphere spells, causing the nontoken Shield Sphere to enter the battlefield, and creating a token copy of it for each time its replicate cost was paid.