Star Shinobi

Thanks to Star Shinobi for sponsoring this encounter!

Spiciness: 4/5

A lot of single target Damage, but not going to TPK.

Feeds about players 3-5, level 5-7

Scales for: Number of Players, Player Level

Ingredients:

• 2 Star Shinobi (Based on the Star Spawn Mangler, MToF)
• X Star Spawn Grue (One Per Player, MToF)

Scale the Save DCs: At level 7, add +1 to their Save DCs.

Preparation

Star Spawn are the demons of aberrations-- Chaotic, Evil, looking to destroy things. But unlike the animalistic, primal demons that use brute force or arcane might, the Star Spawn can be hyper intelligent.

As an example, the Star Spawn Mangler is very stealthy. Between having a +7 to stealth, darkvision, Ambush, AND Shadow Stealth, it already felt like a ninja, so adding the two abilities Time Warp and Substitution Jutsu make it feel way more interesting and "ninja like". Of course, the encounter has to be an ambush as well, so here's the pre-battle prep!
Before the Combat: The Star Shinobi are hiding in shadows (possibly on the walls or columns as they have a climb speed), while the Grue are behind total cover. As the party walks into their trap, they each roll Perception (DC 17) to notice the Shinobi, who are quickly beginning the fight. On a failure, that creature is surprised.
Things you need to know for this fight:

• Any time the Shinobi has advantage on its claw attack, it deals 2d6 extra psychic damage. On a critical, this number would also be doubled (to 4d6).
• If you're surprised, you can't move or take an action on your first turn of the combat, and you can't take a reaction until that turn ends. You may still take a bonus action.
• Recharge X–Y: The notation “Recharge X–Y” means a monster can use a Special ability once, and that ability then has a random chance of recharging during each subsequent round of Combat. At the start of each of the monster’s turns, roll a d6. If the roll is one of the numbers in the Recharge notation, the monster regains the use of the Special ability.

Cooking the Star Spawn Grue

Round 1+: The role of the Grue is straightforward: hit people with Confounding Bite so the Shinobi deal way more damage. Easy peasy. Don't forget their Aura of Madness, so players have disadvantage on the save against the Confounding Bite. Be sure to end your turn near the party as well, to keep that Aura on them.

Cooking the Star Shinobi

As Initiative is Rolled: Time Swap to get a better spot in the initiative! Try to use this on someone within 20ft of a Grue so they have disadvantage on the save.
Round 1: You have advantage on all attacks against people who haven't had a turn, so use Flurry to get close to them (you won't provoke AoOs and can dash as a bonus action), then hit them with SIX Claw attacks from the Flurry. Since you have advantage, you deal the extra psychic damage for a total of about 90 damage Average, assuming no crits. This will likely down a player, maybe two in the first round.
Round 2+: Now that Ambush is offline, we have to get creative on how to get Advantage. Creatures confused by the Grue are easy targets for this, or you can use your bonus action Hide from Shadow Stealth to get advantage on 1 of those attacks. Don't forget to Recharge Flurry and use that again if you can!
Reactions: As a reaction to being the target of an attack roll, you can try to make someone else take that attack for you. If your health is pretty high, try to swap with a party member. There's a chance it fails and you get hit, but there's also a chance that the party hits themselves this way. If you're low on health, it may be better to switch to a Grue or someone who can tank the shot (since they get no save against this and it won't fail).