From Destinypedia, the Destiny wiki
Egon and his unnamed guardian partner went to a presumed casino and found the weapon Monte Carlo. The duo thought they could go and trade it in for a "small fortune" in Glimmer however a group of Fallen came and killed Egon's partner along with their ghost but Egon escaped because his ghost planned an escape route. Egon was then Interrogated by the Vanguard for questions about what happened to his partner.
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