The Giant Wolf Spider as presented in the 5th Edition Monster Manual is perfectly usable monster, but I noticed while reading up on real world wolf spiders that it doesn’t quite capture their flavor. Presented below is my slightly tweaked version, the Giant Wolf Spider (Variant).
This variant is based on the Giant Wolf Spider from the Monster Manual, with the following changes:
Tremorsense: Giant Wolf Spiders and Giant Spiders both have Blindsight listed under their senses. I’m not entirely certain why the designers chose this ability–maybe it is supposed to reflect a spider’s 360 degree vision and excellent sense of touch, or perhaps it is a nod to Spider-Man’s tingly danger-sense. Regardless, I felt that Tremorsense was a better reflection of the wolf spider’s ability to detect nearby prey through vibrations. I kept the range of 10 feet, as that seemed reasonable.
Hunters. Wolf spiders hunt prey or lie in ambush in burrows. To better reflect this, I added the Ambusher trait (found on the Kenku and Doppleganger) as well as a Hidden Ambush reaction. I wanted to capture how they quickly emerge from their hiding places to attack their prey. Giving them Hidden Ambush in the form of a reaction facilitates encounters in which Giant Wolf Spiders lie in wait even after the first round of initiative while still allowing them to get the jump on PCs. The line that says that creatures attacked as a result of the Hidden Ambush are considered surprised allows the Ambusher trait to trigger and makes an exception to the general rule that surprise is determined only once at the beginning of combat and that a creature cannot be surprised again.
It would have been simpler, of course, to just grant advantage on the Hidden Ambush attack, but the use of “surprise” is intentional: it allows the attack to interact with other game abilities related to being surprised. For example, the Alert feat says that a PC cannot be surprised while they are conscious. It is the intention that in this case, the attack granted by Hidden Ambush would not have advantage (because Alert prevents the PC from being surprised).
No Webs. Wolf spiders don’t spin webs (though they do spin silk). As such, I removed Web Sense and Web Walker. The former is replaced by Tremorsense. As for the latter, one could probably argue that being a spider allows the Giant Wolf Spider to walk on webbing regardless of whether or not it can spin them.
Otherwise, the statblock is the same as the base Giant Wolf Spider. The addition and subtraction of a few traits and actions wasn’t enough to warrant changing the Challenge Rating, and the other stats seem reasonable. I considered doubling the Proficiency Bonus added to Perception–real world wolf spiders are noted as having excellent vision and other senses–but I suspect that the fact the Giant Wolf Spider is considered trained in Perception at all (compare with the Giant Spider who is not) is meant to reflect this.
I think these minor changes help better reflect the abilities of the wolf spider, while also distinguishing the Giant Wolf Spider a bit more from the Giant Spider. Whereas the Giant Spider may lie in wait for a victim to be snared in its web, the Giant Wolf Spider hides among debris and in small burrows, waiting for the moment to pounce.