Glak, Very Helpful Assistant

You may sacrifice any number of permanents, discard any number of cards, and reorder any number of graveyards any time you could cast an instant.
Partner
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"Boss, I sorted all of your things, they're in the incinerator."

(Glak's ability is a single special action. If cards enter graveyards you're ordering as part of the action, you choose where they go.)
(Special actions don't use the stack. See rule 116, “Special Actions.”)