Partner with Evie Frye (When this creature enters, target player may put Evie into their hand from their library, then shuffle.)
Whenever one or more Assassins you control deal combat damage to a player, exile up to one target Assassin card or card with freerunning from your graveyard. If you do, copy it. You may cast the copy.
Jacob Frye leads a mono-black Assassin tribal deck that grinds value out of combat. Deploy a wide board of cheap Assassins, connect with combat damage, and use Jacob's trigger to recast key Assassins or freerunning spells from your graveyard for free. You snowball card advantage and recursion while chipping (or stabbing) opponents to death.
Repeatable free recasting of Assassins and freerunning cards generates relentless value once you connect
Mono-black gives access to powerful tutors, recursion, and removal to assemble the gameplan
Partner with Evie Frye effectively gives two commanders' worth of bodies and card selection
Combat-damage trigger fires on any Assassin connecting, not just Jacob, so going wide is rewarded
Needs Assassins to actually deal combat damage, so board wipes and fogs blank the engine
Mono-black means no protective counterspells and limited interaction with enchantments/artifacts
Relatively shallow real Assassin tribal pool can force generic filler creatures
Removing Jacob shuts off the recursion payoff, and the deck can stall without an alpha strike
Loops creatures back to fuel both attacks and graveyard targets for the exile-and-copy ability.
Add fast mana (Sol Ring, Arcane Signet) and efficient black tutors (Demonic Tutor, Vampiric Tutor) to find your enablers faster. Lean into evasion and protection so Jacob's trigger fires every turn, and pick up powerful freerunning cards to exploit the copy ability. Round out interaction with cheap removal and a sacrifice subtheme so blocked or wiped Assassins still convert to value.