Merry, Warden of Isengard

Both commanders start in the command zone, and the remaining 98 cards of your deck are shuffled to become your library.

The second ability represented by the "partner with [name]" keyword modifies the rules for deck construction in the Commander variant and has no function outside of that variant. If a legendary creature card with "partner with [name]" is designated as your commander, the named legendary creature card can also be designated as your commander. For more information on the Commander variant, please visit Wizards.com/Commander.

Note that the target player searches their library (which may be affected by effects such as that of Stranglehold) and that the card they find is revealed, even though these words aren't included in the ability's reminder text.