Karma Orb’s sprite is a reference to sans from Undertale (blue eye and bony smile), as well as the name being a reference to the game mechanic of KARMA. it is also a reference to the concept of karma itself in its description “what goes around comes around” as well as the effect of the orb, petrifying the user if they try to stasis an enemy.
Shield of Pogmur’s projectile sprite and the item’s name is a reference to a popular Twitch emote called PogChamp.
Anubis Necromancer is a reference to the Ancient Egyptian god of mummification/afterlife.
Vengeful Yokai Necromancer is based upon supernatural entities/spirits in Japanese folklore.
These are yet to be released in the game, but:
Skeleton Trumpeter is a reference to the doot doot meme.
Twintailed Vocalist is a reference to the vocaloid Hatsune Miku.
Treacherous Trout is a reference to Fish in the game Nuclear Throne.
Ferret Pet is a reference to the Furret walk meme (and so too is the description).