Halana, Kessig Ranger

You can choose two commanders with partner that are the same color or colors. In Commander Draft, you can even choose two of the same commander with partner if you drafted them. If you do this, make sure you keep the number of times you've cast each from the command zone clear for "commander tax" purposes.

If something refers to your commander while you have two commanders, it refers to one of them of your choice. If you are instructed to perform an action on your commander (e.g. put it from the command zone into your hand due to Command Beacon), you choose one of your commanders at the time the effect happens.

For the creature that entered the battlefield, use its power as Halana's reflexive triggered ability resolves to determine how much damage is dealt. If it's no longer on the battlefield at that time, use its power as it last existed on the battlefield.