What stats does Broken Prototype give?

Broken Prototype grants 100 HP.

Where does Broken Prototype come from in TFT Set 17?

Broken Prototype is a Anima cash-out item.

Yes — Broken Prototype enables a Shield effect.

Combat start: Gain a 15% max Health shield.

anima

Combat start: Gain a 15% max Health shield.

Shield

Grants temporary HP that absorbs damage before the unit's real Health is touched.

Max Health

Grants the unit additional maximum HP, either flat (like +150 Health) or percentage (like +6% max Health). It comes up whenever you stack Giant's Belt items, pick health-boost augments such as Yasuo's Golden Hex or Giant and Mighty, or play Cho'Gath, whose cast permanently raises his own max Health every time he eats an enemy. For the cross-round permanent stat-stacks angle specifically, see the dedicated permanent stat-stacks page.