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Grinding for materials to unlock new characters is a major part of TFD. It usually boils down to repeating the same mission over and over again until you get the blueprint that you want. But, for Hailey, the method is a bit different. The best way to get Hailey materials is by playing the new Invasion Missions.
Gold Tier Rewards Are What Everyone Is Gunning For
Invasion missions are a peculiar new addition to The First Descendant. They are tough solo missions that reward you with materials for researching Hailey. The better “grade” you get, the better the rewards will be. If you manage to get the coveted “Gold” grade, you will get more Hailey materials than usual. The grades are time-based, so players are trying to complete these missions as fast as they can. As with almost all TFD missions, you can choose to restart these Invasion missions, in hopes of getting a better reward, ie, that Gold tier reward. But, how many restarts are too many?
Three is Enough
One player started a Reddit thread on this subject, stating that quitting and restarting more than three times, in hopes of getting the Gold rewards, is a bit of a waste of time. You should settle for the Silver rewards, and keep on playing other missions. The time wasted by restarting the same mission over and over again could be better spent by farming Hailey materials in regular dungeons.
Others agree, but add that if you are very close to getting the Gold, you should restart until you play it right. “If I’m close to the gold and I make a mistake then yeah I’ll reset and go again, but if the boss is tougher than I care to take seriously, I’ll take the silver.” said gamrguypb. “If I know for sure I can get Gold and I [made a mistake] for being greedy, I’m resetting the run, trying again. It’s not that hard, I got 3 gold and silver today, and the silver run was me [messing] around and not particularly caring. I’m halfway on two parts for Hailey, and a third on one, I’ll get her when I get her” added CriticismVirtual7603.
In summary, if you are really close to getting that Gold reward, then by all means, restart until you manage to get it. But if, realistically, you are nowhere close to the Gold tier rewards after a couple of tries, just settle for Silver and carry on. And this is all under the impression that you are looking to unlock Hailey as fast as possible. If not, then take your time.