Sephiria Lightning Boomerang Build: Spellbook Casting Guide

The lightning boomerang spellbook is the one magic build in Sephiria with a documented high-tier clear behind it: a Traditional Chinese Steam guide, updated mid-August 2026, reports final-boss DPS "over 10K without trying, 30K–50K+ with good pickups" on Hard Mode 60. The catch, in the author's own words, is that the power curve is not smooth — the build feels weak until a handful of specific artifacts land, then jumps. This page is that handful, in the order the author takes them.

Like every route on this site it is one player's attributed run, not a ranking — the builds overview explains why we do not publish a tier list.

The idea in one sentence

Cast the Lightning Boomerang spellbook continuously, keep its cooldown near zero with Academy items, keep MP full with the Lake water jug, and stack compasses in a row directly under the boomerang for damage. Everything else is support.

Weapon and costume

The guide recommends three weapons and rules out a fourth:

Costume is a trade-off the author leaves to you. Ghost or Red Cloak keep MP comfortable early but have no lifesteal, which hurts on high tiers; bringing a lifesteal stone through the Wish Fountain instead makes the early floors MP-starved. Frog and Skeleton are also listed as workable.

The core artifacts — take on sight

These are the pieces the build does not function without. The names below are our translation of the guide's Traditional Chinese; where the English item name is confirmed elsewhere we use it, and where it is not we say so.

• Lightning Boomerang spellbook — the main damage source.
• Water Jug (Lake tag) — "without this your damage stops growing and the boomerang cooldown never gets good." It activates at 200 MP, which you reach through the Lake combo bonus plus Broken Branch (+60 max MP) and Sapphire (+33% max MP). The Lake tag also carries the Cup, the only MP-steal artifact the author knows of — take it if you are not on the Ghost costume.
• Hourglass and Pocket Watch (Academy tag) — the two cooldown reducers. "Take on sight; the build is not fun until both are in."
• Meditation Book (Academy) — without it "the late game is very hard to play": casts stall, you get burst down, and you cannot chain casts.
• Compass — as many as you can find, placed in a contiguous row under the boomerang. Each is +35% at the author's count; six in a line is +210%. The tablet and grid rules for "contiguous with nothing in between" apply here exactly.

Secondary damage, all optional: the Lightning Magic Bolt (your only real damage until the boomerang appears, if you did not start Ghost), Thunder Armour and Judgement of Thunder — take them when MP allows.

Pickup priority

The author's order, which we reproduce rather than reorder:

Core artifacts > Magitech ≥ Lake (to 200 MP) ≥ Precision > Academy (non-core) ≥ Elemental and other damage.

• Magitech: spellbooks and lightning damage. Some elemental damage early "makes the run more comfortable."
• Lake: only the water jug and the MP-steal cup really matter; the rest of the tag is low value but you take it for the combo count and the MP ceiling.
• Academy: Meditation Book, Hourglass, Pocket Watch, then anything with combo count or cooldown. The author is specific about why the Crabapple is low priority: its spellbook speed-up is +14 against the Pocket Watch's +80 and the Coin's +30.
• Precision: crit damage and legendaries first.
• Elemental: the Elemental Book first as a secondary base-damage source, the rest for combo count.
• Alchemy: only the Potato, for ignoring enemy defence; the Traveller's Blessing is skippable.

For survivability the author prefers evasion over the Shield Bag's defence route, and notes the Battle Bracelet + Elastic Band combination lets a single dash become near-permanent evasion if you keep landing dodges.

What the DPS numbers mean

The 10K / 30K / 50K figures are the author's final-boss readings on Hard Mode 60, from a recorded run, not from the training dummy. They are not reproducible by us and we have not tried; we print them because they are the only published magnitude for a spellbook build and because the author is candid that they depend on luck — "usually you can still clear with a few pieces missing, it just isn't as satisfying."

Patch notes that touch this build

Nothing in the 1.0.19–1.0.30 line rebalances a lightning spellbook. Two adjacent changes are worth knowing: Green Sawblade (1.0.26) now applies its buff correctly when 30 or more MP is spent in one cast, which matters for a build that burns MP in bursts; and the 1.0.26 preset expansion (7 → 15 slots, with a lock) means you can keep this loadout saved next to a melee one. If you run the staff variant, 1.0.30 changed Flourish Staff so holding attack during a special resumes attacking immediately afterwards.

The stat definitions behind the build — magic damage affects spellbooks only, MP regeneration is per 10 seconds, magic haste at 200% halves cooldowns — come from the Early Access community guide and have not been contradicted by any 1.0 note; we flag them as community-documented rather than developer-published, per our editorial policy.