Resolve and pay for the Inalla trigger from earlier, creating a token copy of Spellseeker and leaving ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) floating.
Shortcut resolving both Inalla's trigger and Spellseeker's ETB, tutoring for Burnt Offering and Finale of Promise, leaving ({B} magic symbol) floating.
Use that mana to cast Finale of Promise with X=1 targeting Unearth and Culling the Weak.
Sacrifice a Spellseeker token to Culling the Weak for ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) and UnearthSpellseeker.
Resolve Spellseeker's ETB and Inalla's trigger, tutoring Entomb and Reanimate into hand.
Entomb and then ReanimateArchaeomancer, leaving ({B} magic symbol) floating.
Resolve Archaeomancer's ETB, returning Burnt Offering from your graveyard to your hand.
Resolve the Inalla trigger from when Archaeomancer ETB'd and return Reanimate to your hand, leaving ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) floating.
ReanimateArchaeomancer and resolve the Inalla trigger, retrieving Burnt Offering and FInale of promise, ({B} magic symbol) floating.
Resolve the Inalla trigger, making a token copy of Archaeomancer with haste and leaving ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) floating.