Foster is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Whenever a creature you control dies, you may pay . If you do, reveal cards from the top of your library until you reveal a creature card. Put that card into your hand and the rest into your graveyard.

How it works : Foster

Original English text — Wizards of the Coast / Scryfall

No additional ruling has been published for this card.

Interactions with other cards

These cards' text mentions Foster.

Doctor Jane Foster

Vigilance (Attacking doesn't cause this creature to tap.) When Doctor Jane Foster enters, return target creature card with mana value 3 or less from your graveyard to your hand. If you gained life this turn, return that card to the battlefield instead.