A NSW Independent Commission Against Corruption is investigating alleged illicit political donations and branch-stacking, spearheaded by the Reformers, a conservative Christian faction among the NSW Liberals.
Prominent players included two brothers of former NSW premier Dominic Perrottet.
Mr Assaf knew Jean-Claude Perrottet through an Opus Dei-run study centre at Redfield College in northwest Sydney.
The Catholic school is in the same local government area, the Hills Shire, where allegations of branch-stacking to benefit the business interests of fugitive property developer Jean Nassif are being investigated.
The now-lobbyist said he was driven by biblical values and found a vehicle to influence political change, chiefly opposition to gay marriage, culminating in co-founding the Reformers.
"I cared more about the faith and values and certain policies, and I just always had a bit of an icky feeling about politics and faction games and all that sort of stuff," Mr Assaf told the commission on Thursday.
"When I joined, there was a bit of a baptism of fire from a factional sense because there was a giant split that occurred within the right."
Under questioning from counsel assisting Peggy Dwyer, he likened the factional infighting to iconic film Braveheart.
"The right faction was like, not sure if you've seen Braveheart, but these warring kingdoms, they would slaughter each other and then every now and then they'd come together for a big fight," Mr Assaf said.
"We wanted people to be loyal to policies not personality."
He later worked at Catholic Schools NSW, the governing body for 600 diocesan schools across the state, where the probe heard he split his time 60-40 between Liberal Party factional horsetrading and his actual duties.
The 30-year-old, who spent a year in a Catholic seminary training to be a priest, rose through the ranks of the party working as a staffer for several ministers, eventually being hired by former prime minister Tony Abbott.
Mr Abbott was voted in as party president in May.
Mr Assaf's testimony comes after claims by former NSW Catholic Schools boss Dallas McInerney that now-federal Liberal leader Angus Taylor agreed to make a series of payments to the Reformers.
Mr Taylor, who is not under investigation by the corruption watchdog, has denied making donations to the ultra-conservative faction.
"I want to shake down Angus for 10K," Mr McInerney wrote to Mr Assaf in a message aired at the inquiry on Tuesday.
The opposition leader said "no payment was made" in the form of a $15,000 "injection" and monthly $3000 donations to the Reformers, as claimed in a text message by former Liberal Party staffer Dylan Whitelaw.
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