Oath of Chandra

When Oath of Chandra enters, it deals 3 damage to target creature an opponent controls.
At the beginning of each end step, if a planeswalker entered the battlefield under your control this turn, Oath of Chandra deals 2 damage to each opponent.

Pioneer Masters

"If it means that people can live in freedom, yeah, I'll keep watch."

Oath of the Gatewatch

When Oath of Chandra enters the battlefield, it deals 3 damage to target creature an opponent controls.
At the beginning of each end step, if a planeswalker entered the battlefield under your control this turn, Oath of Chandra deals 2 damage to each opponent.

Oath of the Gatewatch Promos

Each of the Oaths is legendary: if you control more than one of any particular Oath, you choose one to remain on the battlefield and the others are put into your graveyard.

Even if you control a particular Oath, you can cast another of that Oath to take advantage of its enters-the-battlefield ability. It will enter the battlefield, causing its first ability to trigger. You will then choose one to keep, as detailed above, and then its enters-the-battlefield ability will resolve.

Oath of Chandra’s last ability will trigger even if the planeswalker that entered the battlefield under your control is no longer on the battlefield, no longer under your control, or no longer a planeswalker. This is also true if Oath of Chandra wasn’t on the battlefield when the planeswalker entered.

The last ability triggers only once per turn, even if more than one planeswalker entered the battlefield under your control.

The “legend rule” checks the full names of legendary permanents. You can control Oath of Gideon and Oath of Chandra at the same time, for example.