D&D 5E - Monster Tactics (nightmare)

So a possible scenario might look something like this:
Bad Guys (BG): Nightmare, 1 stronger rider, 2 not as strong along side. All Bad Guys have some type of ranged attack, either bow or spell.

Good Guys: The PCs.

For this illustration imagine the PCs are at the center of a circle. The BGs will initially appear at the 12 o'clock position if looking down on battlefield.

Round 1: BGs appear from Ethereal approximately 80 to 90 feet from party. BGs launch ranged attack at nearest target from readied action.

R2: BGs again launch ranged attack at nearest target. Using readied action Nightmare transports all into Ethereal.

R3. BG reposition to appear at 10 o'clock potion (possible farther depending on movement of PCs)

R4-6: Repeat tactics from previous three rounds.

The BGs will randomly reposition to their left or right in an attempt to keep the PCs from predicting their arrival point. During the initial few rounds the BGs will target the nearest PC. After a few rounds the BGs may switch targets depending on the situation. If any PCs appear to be able to track the BGs in Ethereal, that PC will be targeted. IF any PC (especially a spell caster) becomes separated from the others, the BGs will shift tactics and appear next to the isolated PC and engage in melee combat before returning to Ethereal to continue previous tactics.

Just a quick thought on some hit and run and hit again tactics.

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