So, most of this section will be about farming. If you’re looking for CQ setups, skip down to the bottom of this section and look at the four paragraphs right above the CE recommendations. For farming, though, a brief outline: I’m going to start with Oberon’s super top-end farming potential, and then address different ways he can be used to support various Buster, Arts, and Quick setups, in that order. There’s a lot of overlap in terms of how he works with each card type, but if you’re looking for one in particular, that should help find it.
Let’s start with Oberon’s single best farming partner: Melusine. Melusine/Koyanskaya/Koyanskaya/Oberon can tri-loop with any CEs regardless of enemy composition and has silly good damage in the process. Melusine uses all her skills on turn 1, and both Koyanskayas use their Buster buffs. Turn 2, the Koyanskayas use their batteries, and Melusine uses her NP damage buff. Turn 3, Melusine uses her battery again, and Oberon swaps in and uses all of his buffs. With this setup, Melusine deals 205k damage to wave 3, at neutral, at NP1, with no CE. Against NP levels or Man enemies, this damage skyrockets. Her damage is a lot lower on the first two waves, and she’ll likely need NP levels to farm 90+ as a result, but in exchange she can farm even 1/1/1 nodes and her wave 3 damage is through the roof. Furthermore, since this is CE-less, she can sacrifice a drop CE to run Black Grail in a pinch for extra damage. Melusine is pretty solidly the best farmer in the game now, although she needs both native Koyanskaya and native Oberon to really matter, and she requires plugsuit, which may make her slower than Arts setups for certain nodes. Additionally, her banner timing is deeply unfortunate, coming directly prior to both of the supports she requires.
For a slightly more accessible alternative, you can run Oberon himself. Specifically, Oberon/Koyanskaya/Reines/Koyanskaya. (You can also swap Reines for Castoria or Waver for the same effect, albeit with a slight damage loss). Oberon needs his Mana Loading skill unlocked for this to work, but with it, the rotation looks like this: Turn 1, Oberon starts with 10% charge, he uses his own skills to get to 80%, Reines uses her attack buff to take Oberon to 100%, Koyanskaya uses her Buster buff, and Oberon NPs. Turn 2, Koyanskaya uses her battery and plugs out for the other Koyanskaya, who uses all of her buffs. Oberon NPs again. Turn 3, Oberon uses all of his skills on himself, Reines uses her remaining 30% batteries, and Oberon NPs for big damage. Oberon is generally going to need NP2 to hit damage thresholds against Knights, and you may need to use plugsuit’s attack buff on wave 1 or 2 to push damage a little on those earlier waves, but in exchange you have a Servant who 6-drop farms about half of farming nodes with no RNG. This may be a slightly more appealing setup to target than Melusine’s, despite being weaker overall, as you can pull Koyanskaya and Oberon first, and then go for NP2+ on Oberon if you have quartz leftover.
As a related note, Alter Egos were always an odd class in part because they’re sort of inherently less appealing than just running a Berserker. Pretenders have a similar issue, with the caveat that Alter Egos are harder to counter than Foreigners. That said, now that both AE and Pretender exist, it’s realistically possible to invest in an omnifarmer in each class and therefore have all your farming bases covered (outside of mixed-class nodes). It’s still better in the abstract to just have one Berserker that can do the same thing, but if you don’t love the top farming Berserkers, or if you miss their banners, investing in both an Alter Ego and a Pretender is a viable alternative. This can also be appealing if the comparable Berserkers are less reliable farmers than an available Alter Ego or Pretender. Servants like Oberon and Kiara, for instance, have appeal over their Berserker counterparts due to their more flexible tri-loops, so investing in those two to cover your farming bases is a workable option.
Moving past the guaranteed perfect 6-drop setups, we get to alternative Buster farming teams. There are a couple of ways to approach team-building with Oberon. To start with the obvious, any Buster Servant with at least a 30% battery can tri-loop with Kaleid. It doesn’t even need to be an MLB Kaleid, thanks to Mana Loading. You run DPS/Koyanskaya/Koyanskaya/Oberon, let the DPS NP with Kaleid turn 1, use Koyanskaya’s batteries turn 2, and use the DPS’s battery and Oberon’s batteries and buffs turn 3. This was always possible, but damage used to be an issue, and it used to require a 50% battery and an MLB Kaleid. Now this is more accessible and hits a lot harder, so that’s nice.
Even for Servants without batteries, though, you can enable duo-loop setups with the help of Arash, Habetrot, or Chen Gong. With Arash or Chen Gong, you run Oberon/DPS/Arash (or CG)/Koyanskaya/Koyanskaya. On turn 1, you use Oberon’s AoE battery, and you use his ST battery on Arash or CG. Arash gets to 100% with his battery, and CG gets there with his battery + Mana Loading. Oberon can use his third skill to amp Arash’s or CG’s damage if necessary, or he can hold off so that he or CG can boost the DPS’s NP on wave 3, depending on damage thresholds. Arash or CG NPs, the DPS NPs with Kaleid on wave 2, and the DPS NPs with Koyanskaya on wave 3. This works regardless of the DPS’s skillset, which means any AoE Servant can do this if it has high enough damage. It does require a starting NP charge CE on your DPS, which means it’s going to be a 5-drop setup unless the event CE provides NP charge, but still, if you’ve invested heavily in a given AoE Buster unit, they can probably farm with this setup.
Habetrot is even better for this if she hits damage thresholds. Habetrot doesn’t actually need Oberon’s batteries to use her NP, which means any Buster Servant with a 10% battery can 6-drop farm, provided Habetrot and the DPS deal enough damage. Mana Loading on the DPS, plus Oberon’s batteries, plus 10% charge gets your DPS to their first NP, and Koyanskaya gets them to their second. As an added plus, Habetrot has a hefty NP damage buff, so Oberon still has the option to use his third skill to buff her damage or the DPS’s, as needed.
There are all sorts of possible variations on the above setups, too. The more and better batteries a Servant has, the more flexibility they have to run better CEs, use drop CEs that start with charge, spend buffs on the Arashlike, etc etc. The big takeaway here is that if you like a Servant, you can probably use Oberon to farm with them in a way that is either fully optimal or close to it. It’s pretty silly.
So, that covers Buster. Moving on to Arts, you get a lot of the same. Any Arash, CG, or Habetrot setup that works for Buster also works for Arts under the same conditions (replacing Koyanskaya with Castoria). This means that, as with Buster, you can 5-drop farm anything with your favorite Arts Servants, provided you hit damage thresholds.
The difference here is that 6-drops are more likely to be possible with Arts than with Buster, as you can cover for missing batteries with NP refund. The number of possible ways this can happen makes it difficult to give generic examples, but you can do things like use Oberon to boost Arash to his NP, then use both Castoria Charismas (plus Mana Loading and Oberon’s battery) to get your first DPS NP, after which you only need to refund 60% off wave 2 to NP against wave 3, as you have both Castorias’ second skills ready to go. If your DPS has a battery, the refund threshold is even lower. AoE Arts Servants don’t typically refund much against a single enemy, but two-enemy waves may be doable even for some Servants without batteries, and servants with 50% batteries (like Kiara, Muramasa, and Spishtar) get their wave 3 NPs mostly for free.
Oberon also has real value in Arts triloop farming, as he reduces the amount of refund you need on one wave by 20% relative to a plug Waver or Reines. Habetrot, for example, can farm 1/2/x nodes with Habetrot/Castoria/Castoria/Oberon. Habetrot NPs via her own batteries on wave 1 and Castoria’s on wave 2. She refunds 30% off her wave 2 NP, and Oberon provides the remaining 70% (and also doubles her NP damage buff for good measure). Broadly speaking, Oberon’s extra batteries cover for one wave with one enemy fewer than a Servant would normally be able to farm, which makes 6-drop farming 90+ nodes with Arts Servants a whole lot easier than it was before.
Even Quick setups benefit from Oberon, for similar reasons. Once again, all of the Arashlike setups apply. Any AoE Quick Servant with enough damage can 5-drop farm with Oberon, via the same setups as outlined above with regard to Buster. This can be cool for Servants like Xiang Yu who have good damage with Skadi but very bad loopage. If you have an AoE Quick unit you like and have invested in, you can farm with them.
Oberon also solidifies Quick triloops, for the same reason as he helps Arts. Dantes, for example, gains the ability to farm 2/1/x or 1/2/x nodes with Kaleid, as you have 100% in support batteries to cover the wave of 1 and 70%, thanks to Oberon, to cover the wave of 2. Oberon gets 30% even versus two enemies, so this lets Dantes tri-loop even in cases where he otherwise wouldn’t be able to—and Oberon’s third skill amps wave 3 damage also. Voyager, similarly, has a guaranteed tri-loop with Kaleid (which he already had with Waver, Reines, or Castoria), but with an extra 50% damage buffs on wave 3 (due to Oberon’s third skill) he wouldn’t have had otherwise. Quick is still significantly harder to 6-drop with than Arts is, but 5-drop farming isn’t a huge efficiency drop, and Oberon means Quick can do that just fine.
Oberon has three primary CQ use cases: as a point Servant for Buster stall, as a fight-closing plug buffer, and as a sacrificial charger.
Oberon’s stall use centers on his charges and his NP’s value as a defensive tool. Oberon doesn’t have amazing NP gain in practice, thanks to his deck, but with a pair of supports giving him batteries, Oberon should be able to use his NP fairly regularly, and every turn of NP usage is a turn of nearly-guaranteed protection. Oberon doesn’t work reliably with Merlin, but he does synergize nicely with Castoria teams. Oberon can use his NP to keep the team safe while Castoria’s NP is down, and then Castoria can protect the team while Oberon charges his own NP. Himiko is a natural choice for a third support here, amplifying Castoria’s defensive value while also upping Oberon’s own damage, but Waver and Reines are also both solid choices for prioritizing cycling Oberon’s NP.
In a more conventional supportive context, Oberon is a good Servant to keep in the backline to plug in in emergencies. Oberon’s 70% in total batteries will in many cases be enough to bring a DPS back to NP-readiness, and End of the Dream can let that Servant’s NP break a dangerous bar or close out a fight. If the NP doesn’t end the fight, the skill’s demerit then kicks in and provides a few turns of team protection while forcing the DPS to cycle out in favor of a fresh Servant. Alternatively, Oberon can use his NP and use End of the Dream on himself, contributing a fair bit of damage, locking down the enemy team for a turn, and then keeping the heat off Oberon’s allies until Oberon himself gets knocked out.
The other valuable use case for Oberon in CQs is as, essentially, a Poster Girl Waver without the CE requirement. Oberon can jump-start any team by dropping his charges and then using End of the Dream on himself, drawing enemy fire for up to three turns and dying to make way for another support. This can be useful both for helping to get stall teams through their first few turns of vulnerability and for getting fastburn teams access to an extra support. Very nice utility in general.
Part of Oberon’s whole claim to fame is that he really doesn’t need a CE to do his thing. If Oberon is struggling for damage as a farmer, The Black Grail is far and away his best CE, in part because End of the Dream doubles its impact, but ideally he can run with any random drop CE and do fine. In CQ contexts, Black Grail or Heaven’s Feel are great for DPS Oberon, while Kaleid is probably the best option for support usage (as it ensures Oberon will have Wry Rhyme Goodfellow available for emergencies). Alternatively, if you plan to let Oberon sacrifice himself, you could consider giving him Camlann or a related on-death CE so that Oberon provides one last buff when he eventually dies.
Oberon doesn’t have much need for CCs, as he’s not usually going to be sticking around for long or prioritizing his cards in the interim. Everyone’s Da Vinci-chan can be good for Oberon, as he can use it to both boost his own damage and support an ally—and the NP damage buff is doubled with End of the Dream—but it’s far from a necessity. An added bonus of the Da Vinci CCs is that DPS Oberon prefers to use his cards before his NP anyway, so the usual awkwardness of needing to place cards before his NP is negated. NP gain CCs may be nice for stall uses, too, in order to help Oberon have consistent access to his NP.