The mirror pennant is a large flag ( 40 feet long and 15 feet at the base) designed to be flown from a ship. 

It appears to be made of some kind of highly reflective mirror-like cloth. The cloth is supple and soft, and glows faintly in darkness.

The ensign is highly magical but can only be operated by someone with an affinity toward Mirror Magic.

If the flag is raised by someone with such an affinity they may activate one of the following powers. Only one power may be active at a time and activating a different power requires the flag to completely lowered and re raised, an activity that generally takes ten rounds 

The pennant has three charges, and regains one charge at sunrise.

Any powers activated end at sunrise.

it generally takes 5 rounds to raise the flag, 5 to lower it, and 10 to lower and raise.

Powers

False Colors: 0 charges 

The flag can assume any insignia that the flag raisers has previously seen. Not only will this change the appearances of the pennant but it will alter all other flags and standards the ship is currently flying to be consistent with the pennant. It will also change minor details of the paint scheme to be consistent with that flag 

Steal Appearance: 1 charge

The ship will switch appearances with any ship the flag raisers wishes that the flag raisers has personally seen. This means the flag bearing ship will assume the appearance of the targeted ship and vice versa.  Both ships much be on the same plane of existence. The targeted ship may be no more the 50% smaller or bigger then the ship flying the pennant. 

Similar to the spell Disguise Self the appearance is illusionary and will not withstand any physical inspection.

Close visual inspection may determine the illusion. To discern that you are disguised, a creature can use its action to inspect your appearance and must succeed on an Intelligence (Investigation) check against your spell save DC of 16. Apply +1 to the DC for every 10 feet of distance. 

Mirror Image: 1 Charge

This spell functions identically to the spell Mirror Image except it effects the ship.