In Saturday’s game, I threw a group of insectoid bandits at the party. The bandits were a large number of thri-kreen, bulked up a level with the quick-and-dirty CR-increasing method of increasing their attack bonuses and defenses with +2, plus giving them a better multiattack routine. Two of them had mounts that I adapted off the cuff from the existing giant wasp creature in a similar fashion.
Oh, I’m realizing as I type this that I based the experience reward for the encounter off the listed CRs and not the adjusted ones. Whoops! That’s a risk of such on-the-fly adjustments. I thought the number I wound up with sounded low for the challenge of the fight. I’ll have to make that right at the start of next session.
Anyway. I wasn’t fully satisfied with my wasp adjustment, because the existing giant wasp is a medium creature and one large enough to carry humanoid riders would differ by more than few points’ hit/miss chance. So this afternoon, I’ve taken it upon myself to make a more complete wasp mount write-up. As always, the stat block was created using critterDB.
I started with the existing giant wasp and scaled it up a size, increasing its hit dice size in accordance with the guidelines for such and then giving it a few more. I also increased its Strength and the damage dice of its attacks, to reflect is larger size, then upped its Dexterity and proficiency bonus simply because it’s meant to be a more menacing creature than the baseline giant wasp.
The added traits of Flyby and Lifting Capacity are simply there to make things interesting. One way to have a good mount is to have a creature that is not particularly dangerous or even that compelling on its own, but which when ridden by another creature almost exponentially enhances its deadliness. A flying mount that can avoid opportunity attacks hits that niche, even before you add a wicked poisonous sting.
The “lifting capacity” trait is mainly there for story/non-combat purposes (giant flying wasp abductions!) rather than in-combat uses. As appealing as many people seem to find “drop them from great heights” as a combat tactic, round-by-round it’s almost certainly going to be better to have the wasp and rider make flyby attacks, particularly if the rider has multiattack.