I spent 3 hours putting my players through a tortuous fight against an invisible enemy and the freaks loved it. They were running in circles trying to find and counter it, only to get lured into aggroing and even harder encounter, at which point they fled. They got a piddly amount of xp for the handful of PL-4 enemies they downed along the way, then spent the last hour of the session reading rules to prepare for round 3.
All the invisible bastard did was hit and run, eating up their resources and wasting their time. We finished the session with them walking back into the exact setup they encountered almost 2 sessions ago when they first met it, and yet they’re excited to face it again next week.
The last time my players were this excited about an enemy was fighting the Lamia sisters in Rise of the Runelords, who would dimension door away from fights they were losing. The players went absolutely wild with conspiracies and preparation for future encounters. Generally I struggle to get them to look at anything outside of sessions, while an enemy that runs away will even get the ADHD one to pour over lists of equipment.
So next time you want a villain to be memorable, just walk away. Mid fight, when it looks like the party are starting to get the villain on the ropes, just peace out. Say “nah man, I need some backup”. And then when the backup dies, just peace out again. Buh-bye. You can do it for months without them tiring.
Generally, subverting the assumed framework/linguistic disparity between the actions of player actors and the actions of non-player actors is sort of a monkey-brain way to cause people to lock-in. There’s an unassumed air of “we are active so we know how to disengage but they are responsive so they will engage until we stop engaging.” When you flip that, you get the “wait… no?” neuron fire and that immediately sends people into heightened awareness, as when one thing is wrong, what else is wrong?
One example (non-TTRPG) of this that tends to catch people in the same way is in Undertale when the assumedly-disconnected interface of “saving and loading the game” does not truly grant you the choice-consequence decoupling that is an inferred assumption of it.
We’re just kind of built that way
take Pokémon, where you’re granted a pharmaceutical smorgasbord—up-to-and-including bringing a Pokémon back from unconsciousness at full capabilities—but the second your opponent uses a potion it’s like the NPC has personally offended you.
I keep pointing out my players have like 5 bullshit abilities each, but apparently I’m the bad guy because the gug’s bullshit ability is to make 4 attacks at no MAP and crit the entire party at once.
A good villain has also been preparing for the fight. I often like to have an NPC who tries to get in with the party and that NPC relays information to the boss regarding combat tactics
Plus it’s great for roleplay when and if the mole is discovered
My last couple of sneaky villains did prepare to target the party’s specific weaknesses, but then the bastards rolled really well and almost completely shrugged off the debuffs.
Stupid Swarm-that-Walks got built up as (and had the stats of) an incredibly dangerous and calculating enemy, and even with them playing right into his hands at the start of the battle he just couldn’t land any spells. I was really proud of setting them up too, they’d latched onto the undead guards he’d created so didn’t realise he’d also animated the tableware until it was too late. When he opened the door they were stuck in aoe grouping for a set of mental spells that should have crippled them, but they wouldn’t stop rolling over a 15 on the saves.