Cached Defenses — ruling 1

Bolster itself doesn’t target any creature, though some spells and abilities that bolster may have other effects that target creatures. For example, you could put counters on a creature with protection from white with Abzan Skycaptain’s bolster ability.

Cached Defenses — ruling 2

You determine which creature to put counters on as the spell or ability that instructs you to bolster resolves.

Cached Defenses : règles, fonctionnement et interactions (MTG)

Cached Defenses 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

Bolster 3. (Choose a creature with the least toughness among creatures you control and put three +1/+1 counters on it.)

How it works : Cached Defenses

Original English text — Wizards of the Coast / Scryfall

#1November 24, 2014· Wizards of the Coast
Bolster itself doesn’t target any creature, though some spells and abilities that bolster may have other effects that target creatures. For example, you could put counters on a creature with protection from white with Abzan Skycaptain’s bolster ability.
No other card is named in this ruling.
#2November 24, 2014· Wizards of the Coast
You determine which creature to put counters on as the spell or ability that instructs you to bolster resolves.
No other card is named in this ruling.