I don't particularly care about this. It makes for an interesting and unique encounter. Also, the implications are that the phase spider matriarch is a high elf worshipper of Lloth that transformed herself into a unique monster, so plenty of explanation there.
The Spider Matriarch is one thing. She was a mage who could potentially still cast magic. So, her using Ethereal Jaunt and Misty Step to port across greater distances makes more sense. She could even be explained as using Poison Spray or something of that nature to blast adventurers with poison. I'm fine with her being buffed and powerful.
What I don't like is the Phase Spider minions doing the same thing. That makes Phase Spiders not Phase Spiders. That makes them strange variants also, and that's just weird and unnecessary and it takes away from them being what they truly are. They should be melee brawlers, not ranged teleport mages flying around the level killing people from above.
The point of this entire thread is that when Larian does all these variations to these monsters, they take away from what these monsters truly are. A Phase Spider is no longer a Phase Spider if it is porting hundreds of feet every round from one platform to another as if they are super-powered mages with lots of spell slots casting Misty Step at 3 times the spell's normal abilities to teleport someone. Phase Spiders, by their created nature in D&D, are melee combat assassins. They use Bonus action to vanish from the board so players can't hit them. Then they creep up on them and port back into reality to strike. Remain there for a round and disappear again. They are ninja assassins, not ranged combat poison-spitters.
Likewise, Intellect Devourers are not actually brutes for Mind Flayers. They are also ninja assassins who are supposed to attack lone enemies. They are meant to pop out of nowhere and attack single travelers. Their entire purpose is to devour the person's brain and steal their bodies and act like the person. They take on all of that person's intelligence and memories and everything. They pretend to be that person and then lure other victims into traps with other Intellect Devourers. What Larian has turned them into is some sort of grunt melee attack force for Mind Flayers who simply run up to PCs and swipe them with claws. They don't devour minds and they don't steal their bodies and turn them against their allies.
Now, that said, it would be a sucky game indeed if an intellect devourer ate your MC's brain and then took him/her over. To explain them not doing this part, the tadpole would maybe prevent them. So that makes sense. BUT, the point is, then don't use Intellect Devourers for these encounters. Instead, if you really want to throw a CR 2 enemy at your party of 1 MC and maybe Shadowheart, throw a Grick at them. HP 27, AC 14, Resistant to Bludgeoning, Piercing, Slashing, has multiattack and tentacles and a beak, so it deals some serious damage with +4 to Hit. Almost the same as Intellect Devourer stats but without the Devour Intellect ability and Body Thief. Thus, you still have relatively the same encounter but with a monster that has appropriate 5e stats. You aren't robbing the monster of what makes it what it is.
Or! Better yet, a better fight for a level 2 pair, 1 MC and Shadowheart, would be 2 or 3 Kuo-Toas. They are more grunt Mind Flayer minions. They have AC 13, HP 18, aren't resistant to anything, and they only get 1 attack each round. Besides that, they are sensitive to Sunlight, so they would get disadvantage on attack rolls. Making 2 or 3 Kuo-Toas a more fair fight for a level 1 or 2 pair of heroes at such an early stage in the game.
And THAT is the main point. Throw something more reasonable against the player than 3 Intellect Devourers against 2 characters right away on the beach. The issue we are having is that instead of Larian throwing 2-3 Kuo-Toas, or something similar, at the PC and 1 party member, they are throwing 3 Intellect Devourers and then severely nerfing the monsters so they aren't actually genuine Intellect Devourers. D&D has SO many monsters that Larian could use. Why nerf a monster to make it fit when you could just put a different monster in there and have it work far better for the scenario?
Even if you are using Intellect Devourers as a placeholder for Kuo-Toas, or whatever, at least let us, the players, know that you are doing so for EA. You know, a simple message like, "Hey folks. Just so you know, don't get too bent out of shape that we're using Intellect Devourers in this scene. In the end, we plan on using Kuo-Toas instead. We just don't have models and stats built in yet for them. So sit tight. This is only temporary. We'll be giving you more appropriate monsters later. Promise."
