Diverge is where you earn the right to be wrong — loudly, productively, and without apology.
The purpose of this phase is volume before quality. You're filling the idea well before you start drinking from it. Alternate reality exercises get people out of their own heads. Roleplay gets them into someone else's. Free expression means no editing, no filtering, no "that won't work" before the idea even lands.
Group collaboration here doesn't mean committee decision-making. It means collective imagination. You pool the strange, the practical, the ridiculous, and the inspired — and you see what survives contact with reality.
The constraint is: you don't pick anything yet. That comes later. Right now, you diverge.