I'm looking to add Spindle Drones from Blackstone Fortress into a Wrath & Glory one-shot I'm planning. It's meant to be a dungeon crawl inside of a blackstone facility, somewhat similar to a fortress but built into a planet (and no planet-killing weaponry, more like a research facility). And I'd like to have it being guarded by Spindle Drones.
Going off the stats of a Drone from its 40k datasheet, it's essentially a space marine scout with a short-range gun that steadily grows stronger. I don't necessarily want my players to be fighting an ever-growing amount of Space Marines (especially since this will probably be only tier 2 or 3). So I'm thinking I'll use the W&G stats of a Guardsman instead. And maybe have them grow more durable and more accurate as the threat level rises and/or the party gets closer to the end. Same with their pulse(?) weapon. Start it off as the equivalent of a lasgun, then threat level rises and it grows stronger.
After that, I'm not entirely sure where to go with it. Other than its threat level rising, what kinds of special rules do I give them? They obviously fly, I would probably say they'd be immune to things like Fear and other similar effects... the Blackstone Fortress lore I believe says they meld back into the blackstone walls once they're destroyed, so maybe allow them to come from the blackstone walls?
What do you guys think? Am I right on the money with this? Or should I completely readjust?