Ark is in a late stage in its development where we have highly efficient methods of travel, DPS, resource harvesting, etc, so I felt like there was no need to create something that already fills these niches, as it will either outperform or be outperformed by existing creatures. The idea behind this tame is to significantly enhance dinos that already have their niches and spice up otherwise mundane activities, while posing a risk anytime they're used.
Found deep inside underwater caves (or general deep sea areas on maps without these caves), the Pohlsepia is an intelligent albeit highly venomous mollusk. It's skittish and will swim away from approaching players, but if a player/tame stays close to it for too long, it'll bite. The venom doesn't directly harm its target; instead it consists of a stimulant that buffs the melee damage of the target while increasing the damage it takes by the same factor.
Resembles a cross between its prehistoric concept and a modern blue ringed octopus, while also glowing in the dark.
When tamed, it can sit on a player's shoulder and last for a long time out of water (can be hydrated with water containers). Players can either coax it into applying its venom to their tames or extract it for external use. They also make great pets with their striking, adorable appearance and bioluminescence as they peacefully swim around their underwater pens.
When prompted, the Pohlsepia will detach from your shoulder and latch onto your mounted tame like a Noglin, and inject it with one of two types of venom: a stimulant or a relaxant. The color of its rings indicate which "mode" it's currently in. The stimulant has the aforementioned affects in that it increases damage dealt, damage taken, and movement speed, while the relaxant does the exact opposite: slowing the creature and reducing the damage dealt and taken. However, the player can complete a minigame to constantly inject their mounted tame and multiply these values even further! Fail the minigame and your tame will take heavy damage over time as you maladminister the toxins. Armor piercing damage is not altered by the venom.
You can also extract both types of venom to apply to unmounted tames, as well as yourself! For players, this will also affect reload speed, allowing them to shoot faster when affected by the stimulant venom (soloable Genesis alpha gauntlets?). Maybe be able to manually control it to latch onto other tames that would benefit from damage resistance/damage dealing multipliers?
The idea behind these features is to create a high risk/high reward tame that speeds up PvE dino-to-dino combat, spices up land traversal, as well as playing a role in PvP tanking/DPS. One might think the damage dealt/taken multipliers will cancel each other out. However, this isn't the case as skilled players can generally avoid getting hit too often and bring fights to a conclusion with the damage boost. Also, this is an alternative to having to tame different dinos for specific roles, now you can have one dino species serving as both tanks and damage dealers, by strategically applying venom doses! Its ineffectiveness against armor piercing damage might prevent tanks from being too strong in PvP, where therizinos and mantises with clubs can counter the relaxant's effects. The increased movement speed will simplify land traversal, should players succeed the risky minigame, simultaneously providing players with something interesting to do during otherwise mundane map traversal.
Swim up to it and feed it an Ammonite Bile while its swimming away, before it bites you. It will bite you anyway, but its curiosity is piqued and it will follow you. While envenomed, kill as many creatures as you can and feed/pet it throughout. This method is similar to an Amargasaurus but without the tediousness of it aggro-ing onto other creatures and getting itself killed.
During the process, you may kill creatures with a mount as well. In fact, while mounted, the wild Pohlsepia will automatically latch onto your mount like a Noglin and you're free to kill things without waiting for it to catch up! Of course, you still have to interact with it occasionally, at which point it will automatically detach when you dismount.