Biomass comes back. It generates slowly over time up to a certain limit and there is no other way to "earn" biomass. There is also no way to bypass the biomass requirement for agents. You can increase both the rate of generation and the maximum amount you can have at a time... via microtransations exclusively.
Multiple virtual ingame currencies known as Norn Points, Grendel Gold and Ettin Crystals. You need varying amounts of each to perform even the most basic ingame functions. NP must be purchased with real-world money. There is no way to earn GG apart from watching un-mutable, bandwidth-intensive ads for horrendous mobile games and their even more horrendous knockoffs. EC are gained by playing demos of said mobile games. Each time you perform an action (feeding a creature, hatching an egg) it becomes more expensive. Eventually the game becomes unplayable due to the decillions of NP, GG and EC required to do anything.
Edit: You can also reset the game to earn legacy points that make the game marginally more playable. Doing this will wipe out your entire population, and there's no way to export creatures or save their genomes.
Wait timers, loot boxes, micro-transactions, bloated spying DRM that prevents mods from functioning at all and requires an always online connection! Honestly, this all just applies to any game at all...
To mess with creatures, you have to control a shee avatar and walk to them. Then you have to manual control your hand to pet or slap them. Also the command line cannot be used and you cannot teleport anywhere. You don't have an inventory and can only carry 2 things at once.
You know...wait...nevermind... wait...no...umm...maybe later...
It's always online, and other players can sabotage your world and get rewarded for doing so. You could just suck it up and deal with your favorite creature being dead or the hyper-aggressive grendels that were released into your population, or you could pay a fee to reverse the damage...
There's a really nice breed you can only unlock by giving the game (or "game" a five star review
There's a linear story mode that gets far more dev time and attention than the sandbox mode. The story mode gets just about all of the lore wrong and really only exists to emotionally manipulate you into buying microtransactions so you don't have to see the poor norns' sad faces
Norns become as intelligent and self-aware as humans. They understand their 2D world is simply a simulation, but can't express it beyond "em tired." They curse the developers for envisioning this hell, and us for enabling it.
(The nightmare to you as a player is in the ethics of the situation.)