Comments from the Finger: Arachnoidman, Arachnoidman, does whatever a spider can (without violating copyright). It's true! You too can play as Spiderman in 5e, provided that noone tells Marvel's lawyers.
A life-changing event, perhaps being cursed by a drider warlock or bring bitten by a dangerously transmuted arachnid, has imbued you with the properties of a spider.
Beginning when you select this archetype at 3rd level, you are constantly under the effects of the spell spider climb.
At 3rd level, you can't be surprised and have advantage on initiative rolls.
Starting at 9th level, you can cast the spell web without expending a spell slot or spell components. Alternatively, you can expend a use of this spell to create a long, think rope of web anchored to a location high above you, which you can use to swing at double your movement speed, making an attack with advantage at the end of your swing.
You can cast this spell a number of times equal to your Dexterity modifier. You regain all expended uses of this spell when you finish a long rest.
Save DCs. Some of the features in this subclass call for saving throws. The saving throw DC is calculated as 8 + your proficiency bonus + your Constitution modifier.
Beginning at 13th level, you have advantage on Dexterity (Stealth) checks made to hide or to move silently while climbing on vertical surfaces or ceilings.
At 17th level, you have grown a hideous set of opposable, venom-injecting fangs. Instead of dealing additional damage when you make a Sneak Attack against a creature, you can instead attempt to inject them with a paralytic poison. The target of the Sneak Attack must make a Constitution saving throw or be paralyzed until the beginning of your next turn.