I'm struggling with the Sword Spiders in this game as well. They aren't really quite what I'd expect to see based on the original BG series games. What do you all think of this?:
The DM chose to use Giant Spider stats, modifying them to match the description of Sword Spiders from the previous Baldur’s Gate game series.
The sword spider was one of three different high-level spiders encountered in the Baldur's Gate region. The other two were the Wraith Spider and Phase Spider. They were fairly rare, usually only found within the depths of various forests. Sword spiders ranged in lengths of 12 to 20 feet in diameter and heights of 12 to 13 feet. They had sleek but hairy black bodies with dark-brown-striped fur. Their legs had chitinous plates with sharp ridges that resembled blades. This spider was naturally under a Normal Haste effect. (excerpt from fandom.)
This meant that they were considered to have haste at all times. As a result, their AC was 16 (+2 for haste). They also had Multiattack. This gave them the ability to attack with their Bite and their two front legs as 1 Action and then attack with their two front legs again as a second, hasted, Action. Thus, they would get 3 attacks per round (note: the damage for the leg attacks factors in striking with both front sword-legs).
For attack stats, Bite was +6 to hit, reach 5 ft, Damage 1d8+4 piercing. They also poisoned their victims. A DC 11 Con save would be rolled dealing 2d8 poison damage on a failed save and half for a success. In addition, like other spiders, if the poison damage reduced the target to 0 HP, the target would be stable but poisoned for 1 hour, even after regaining HP, and was paralyzed while poisoned in that way.
Besides Bite, they could use their front legs to do a melee attack as if they wielded swords. This was with +6 to Hit, reach 5 feet, Damage 2d6+4 slashing (just like a bear’s claws). As if that wasn’t enough, as an Action, the sword spider could use a special attack called Pounce. It could run at least 10 feet and jump into the air and bring its legs together to impale an enemy. This was considered an Athletics roll, similar to Shove. The sword spider would make an Athletics roll against the target’s Acrobatics roll. If the sword spider rolled lower, it missed the target altogether. If it rolled equal to or higher, it hit and dealt 3d6+4 damage to the target, knocking the target prone.
Finally, they had 4d10+4 HP, Strength 16, Dex 16, Con 12, Int 2, Wis 11, Cha 4, Athletics +7, Blindsight 10 feet, darkvision 60 feet, Spider Climb, Web Sense, and Web Walker. And, since they were considered hasted, they could move 60 feet without using an Action and 120 feet with Dash. They were truly formidable enemies.
