Arknights "Yesterday's Sea" SideStory Preview and October 2026 Sanity Plan
This guide pulls together the 2026-10-03 official activity preview and the 2026-09-25 Producer's Letter #69 to break down the launch cadence, the likely Iberia-style wave structure, operator priorities, and a Sanity budget. Timing comes from published notices; any numbers are ranges based on past events and should be confirmed against the official announcement. Written for Doctors who have cleared the main story and are prepping for the October event. (Guides are also archived in the GameHub guide section.)
Applicable version: current as of the 2026-10-03 update (Arknights has no version-number system; the official notice date is the time anchor)
Arknights "Yesterday's Sea" event info and launch cadence
What the official site has confirmed
The homepage posted "[Activity Preview] SideStory 'Yesterday's Sea' limited-time event opens soon" on 2026-10-03 . Just before that, the studio published an emergency-update notice on 2026-09-29 16:00 and Producer's Letter #69 on 2026-09-25 . Based on the last two years of scheduling, an activity opens roughly 3 to 7 days after the preview drops, so treat early-to-mid October as the window (estimate; confirm with the official notice).
Estimating event length and the shop window
Across the last three SideStories, the main event ran about 14 days with the shop staying open roughly 3 extra days . The two weeks that matter are the front half: clear first-time and fixed stages in week one, then farm material stages in week two. Treat the shop deadline as hard, not soft.
Arknights "Yesterday's Sea" stage mechanics: reading the Iberia wave structure
Why Iberia likely means multi-wave pressure
Iberia is Arknights' long-running coastal region, and past events in it used a two-lane structure of ground push plus air harassment . Expect at least one air-pressure lane with short gaps between waves.
Splitting high ground and ground
Ground units stall melee waves and soak the first push; high-ground units clear air and ranged threats. The steady three-part layout places a high-block Defender at the front, a DPS Guard mid-field, and a Sniper plus AoE Caster on high ground at the back (trade-off reasoning: concentrating limited deploy slots on high-ground DPS that covers both ground and air beats spreading them evenly).
Arknights "Yesterday's Sea" operator priorities
Three roles worth maxing first
Priority order is AoE Caster (clears multi-target and air), high-ground Sniper (single-target burst and long-range picks), then high-block Defender (holding the line). Elite 2 needs chips and Polymerization Agent; keep at least 18 of the mid-to-high tier materials each before the event (estimate; check the official material table).
What you can skip
Pure single-target melee DPS without anti-air is poor value in this predicted wave structure; unless you already have it built, don't raise it just for this event (trade-off reasoning: in multi-wave stages, clear speed beats single-target damage ceilings).
Arknights October Sanity and Orundum budget
| Window | Sanity goes to | Orundum handling | Why |
|---|---|---|---|
| 3 days before | Hold above 1,200 | Claim, don't spend | Leaves room for week-one grinding |
| Week one | First-time and fixed stages | Depends on banners | First-clear rewards are one-time |
| Week two | Material farming | Keep 1,800 buffer | Covers the mid-month second banner |
Sanity: stockpile first, spend later
Filling near the cap before launch is the cheapest way to boost week one. At roughly 240 Sanity of natural regen per day, starting 3 days early frees about 720 extra points for the event.
Orundum and banner choices
October usually brings two banners. To chase both, at 6,000 Orundum per ten-pull you need at least 18,000 banked to call it safe (estimate). If resources are tight, lock one banner and move the rest into operator investment.
Arknights other October content at a glance
Vector Breakthrough #3 and targeted selection
Alongside "Yesterday's Sea", early October adds "Vector Breakthrough #3" and a targeted-selection banner. The selection banner lets you lock three of six six-stars; pick by roster gaps, not by tier lists.
Visual Museum and Integrated Strategies
Late month should bring a "Visual Museum"-style drop and an Integrated Strategies expansion. Both are low-Sanity and work well as pacing between events.
Sanity math for a 14-day window
If the main event runs roughly 14 days and the shop stays open 3 more , a 1,200 opening balance covers about five days of full farming at 240 Sanity per day. Do not dump the whole bank on day one; pace it so week two's material grind still has reserves (trade-off reasoning). Players who also want the Vector Breakthrough #3 rewards should carve out roughly 200 to 300 Sanity before the SideStory opens, since those stages lock when the next cycle starts.
Reading patch dates instead of guessing
Two dates anchor this plan: the 2026-10-03 preview notice and the 2026-09-25 Producer's Letter . Treating the preview as the clock start, an early-to-mid October open is the conservative read. If the official notice later shows a different day, shift the whole schedule by that delta rather than improvising Sanity spends.
What to bank before day one
Keep 18 or more mid-to-high tier elite materials per core operator so you are not farming chips mid-event. Put the AoE Caster and high-ground Sniper on the shortlist first, and treat any pure single-target melee pick as optional. That way the event itself becomes execution rather than a scramble for levels.
Arknights "Yesterday's Sea" FAQ
Q: When does Arknights "Yesterday's Sea" start?
A: The official site posted the preview on 2026-10-03; based on history it opens about 3 to 7 days later, likely early-to-mid October.
Q: How much Sanity should I bank before launch?
A: Aim for at least 1,200; at about 240 Sanity of daily regen, starting 3 days early frees roughly 720 extra points.
Q: Which operators should I raise first?
A: Prioritize AoE Casters and high-ground Snipers; keep at least 18 mid-to-high tier elite materials each, and confirm exact counts against the official material table.
Q: Should I pull new operators for the event?
A: If your roster already covers anti-air and multi-target, skip it; to chase both October banners you need at least 18,000 Orundum banked.
Action checklist
- Log in daily and claim dailies so Sanity stays above 1,200.
- Three days out, lock your AoE Caster and high-ground Sniper and bank 18+ materials each.
- Week one: first-time and fixed stages only. Week two: farm materials.
- Treat Orundum as one-banner-only and keep an 1,800 buffer.
- Watch the official notice for the exact open time rather than trusting the window.
Game Guides
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- Palworld 1.0.5 Breeding Guide: Passive Inheritance Pools, Four-Slot Combos and Work Suitability Roles
Palworld is currently on v1.0.5 (2026-09-15). Since the 1.0 launch on 2026-07-10 ended early access, the Pal roster has grown to 287, the player level cap has risen from 65 to 80, and two new systems, Awakening and Mutation, have joined the game . The breeding rules themselves did not change: an egg inherits from the combined passive pool of both parents, every Pal carries at most 4 passives, and the reliable way to hand a specific trait to a child is to have both parents carry it.
- Reverse: 1999 4.0.0 Dongzhi Team Building: Huntmarked Witch Crossbow Rotation, Friend Support and Mane Bulletin Clears
two new Dongzhi characters plus a generalist support such as Little Rhiannon and a generalist sustain slot such as Marcia, Riddle or J produce a squad that performs in Mane Bulletin and Spotlight Flashback alike The patch went live on 2026-09-24 and the official site lists 4.0.0 as the current version . This piece covers team building, rotation and reward order only, with rules and rewards taken from official announcements. Applicable version: 4.0.0 "Gatekeeper" (launched 2026-09-24)
- Love and Deepspace Midnight Sleepless Guide: Rank 1 Outfit Unlock, the 75% Wish Split and Event Shop Priorities
Love and Deepspace limited banner for the Midnight Sleepless event opened after the 2026-09-22 update and closes at 04:59 on 2026-10-10. You pick 3 of the 5 limited-5-star Memoria, and the ones you pick take 75% of the 5-star drop rate while the unselected event Memoria and the permanent pool split the remaining 25%. The Moonlit Pour event shop runs a day longer, closing at 04:59 on 2026-10-11.
- Honkai Star Rail 4.6 Pearl Team Guide: Elation Resource Loop, DEF Scaling and Light Cone Priorities
Pearl, the Elation-path 5-star Ice character added in Honkai Star Rail 4.6, is unusual because her kit scales largely off DEF rather than ATK, and her Ultimate advances allies and generates the Elation resource. She does not replace a damage dealer so much as the survival-plus-tempo slot, and that distinction decides which teams she actually improves. Pearl is available for the whole of 4.6, with Feiying rerunning in the first half and Thousand-Forged Blade in the second . Version 4.6 "Dance With the Beast Before Moonrise" went live on 2026-09-28 . The official announcement does not publish every multiplier, so figures that depend on exact scaling are marked as subject to the official notice, while team and rotation logic comes from mechanics disclosed in the version preview. Applicable version: 4.6 "Dance With the Beast Before Moonrise" 
- Genshin Impact 7.1 Visner Build Guide: Star Swirl Teams, Sacrificial Blade Stacking and Constellation Value
Visner, added in Genshin Impact 7.1, is a 5-star Anemo sword user built as a Star Swirl main DPS. Her Skill enters an empowered state that applies Anemo infusion and grants two stacks of Sword Qi, and her special Skill climbs through three tiers, with the tier-three cast summoning an extra Spirit Blade hit. In my own testing, a C0 Visner with her signature cleared a single-target ice-coffin setup in about 60 seconds, against roughly 90 seconds for a C0 Dreamweaver Mizuki and about 65 seconds at Mizuki C2. So C0 plus signature edges out C2 Mizuki, but not by a landslide. Version 7.1 "Requiem Toward the Underworld" launched on 2026-09-23, with the banner set boosting Visner and Vaanisa across two wish periods. Every figure below carries its source. Applicable version: 7.1 "Requiem Toward the Underworld" 
- Wuthering Waves 3.7 Heart Build Guide: Dreamward Heart Echoes, Dual-Mode Rotation and Resonance Chain Picks
Heart, the Sentinel added in Wuthering Waves 3.7, is a 5-star Conducto Rectifier main DPS whose damage is almost entirely Resonance Skill damage. Repeated testing puts the finished panel at 2400+ ATK, 78% to 85% CRIT Rate, 270% to 280% CRIT DMG and 130%+ Resonance Efficiency. Her key Resonance Chain nodes are 0, 2, 3 and 6, and node 2 is the breakpoint that fixes the rotation and the multipliers at the same time. Version 3.7 "Mirror-Locked Illusions, Heart-Illuminated Dust" finished maintenance between 04:00 and 11:00 on 2026-09-30, with compensation of 300 Astrite and 2 Crystal Solvents . The official site is a JS-rendered SPA, so every figure below carries its source and should be confirmed against the official notice and in-game values. Applicable version: 3.7 "Mirror-Locked Illusions, Heart-Illuminated Dust" 
- Zenless Zone Zero 3.2 Claret Build Guide: Vanguard Defense Scaling, Crimson Yearning W-Engine and Drive Disc Stats
Claret, Zenless Zone Zero 3.2 first Vanguard agent, scales every damage multiplier off DEF. ATK rolls and normal CRIT DMG rolls do nothing for her; once CRIT Rate passes 100%, every extra point feeds a second critical roll called Sharp Crit. The build order is therefore: stack DEF first, balance CRIT Rate second, and only then chase CRIT DMG. Version 3.2 launched on 2026-09-09 and introduced Vanguard as the fifth combat speciality after Attack, Stun, Support and Anomaly. This guide breaks Claret down into mechanics, W-Engine choice, Drive Disc stats, material list and three team templates, with sources marked throughout. Applicable version: 3.2 "Her Hidden Past"