Spiders. Why'd it have to be spiders? Tara warned me there'd be days like these. Most rooms will have spiders and spider eggs. Smashing a spider egg sac releases 1-3 baby spiders. They are not very strong but if you are busy with the big ones the babies may get past your guard!
Webs hanging across openings may not be walked through without destroying them first.
Egg sacs broken after Zxyzzrx is dead will not hatch babies.
At the first hallway junction, if you go to the right and around the bookcase there is a room with spider eggs a Treasure Chest. It's a trap! Opening the wood chest (empty) locks the door and summons a spider. Good news, killing the spider makes a metal chest appear where the spider spawned.
Left at the first junction, halfway down the hall you will encounter Yyaiayt, but only in Abyss mode.