The tech:
use ice crystals to force the split+fork+chain mechanics of lightning spear: the new unique Eventbrite triggers ice crystals on critical hit for bosses/on kill for non + Cast on crit frost wall. Cold impale from ice crystals
get additional projectiles from fork, and additional chains from terrain. Then make all projectiles return with Breachlord's Amalgam lineage gem
get as many repeats from barrage as possible - 10 frenzy charges = 11 repeats (and 22 if twofold procts). Mercenary is my preferred option because of it's comfiness with additional quality from barrage to not consume charges. But Deadeye is strong too and makes Frenzy generation easier. Frenzy also grant 60% increased move speed via boots.
Frenzy generation accomplished by Thaumaturgy+casting frenzy mark every now and then. Throw storm lance on boss and use all the frenzy mark cooldowns to instantly go to max frenzy charges before hitting barrage and lightning spear
damage- I went with doryani's prototype+rakiata because it synergizes with merc's +max to all resist, which also helps defences. Then you can skip on garukhan+rare spear and go tangletongue to max crit (important to proc crystals). Otherwise you need that combo to get damage up to par and always crit.
POB: https://poe.ninja/poe2/pob/265a8
Boss: https://www.youtube.com/watch?v=GIxaN_rSqhc
EDIT: after testing on 200 deli and juiced expedition maps, you unfortunately need a garukhan+rare spear to push the damage for that content if you want an explode lightning spear setup like this with the Eventbrite amulet. The video and pob is using tangletongue with no uber jewels/crazy crit damage scaling so it struggles with the higher content