How the hell are you level 167? Just from the exp from macroing cores?
No, only highest score on any fields counts towards your total. But it helps a lot to be able to casually throws around hundreds of shadow cores on every field.
If you want a simple recipe, first download autohotkey and make a macro to farm shadow cores from F1 and sell any fragments it drops. When I clocked mine back at level 60 something, it generated about 200 shadow cores every 11 minutes. Leave it on overnight.
Unlock glaring. It doubles the shadow core cost of every trait, in exchange for giving you .7 multiplier instead of .3. Haste, Beacon Storm and Mana Lock all at 7 on Looming mode costs 84 shadow cores and gives a 7.3x xp multiplier at relatively low amount of actual difficulty provided you base a starter mana pool large enough to survive receiving no mana for the first few waves. Same traits on glaring costs 168 and gives a 16.2x multiplier. If you can't do glaring yet, and you're at least level 60 or so you should be able to quickly and easily spam though any field on tiles E, F, I and probably H just by placing a couple towers and armor traps, setting it to fast mode and quickly duplicating/upgrading as you collect mana, pressing next wave before each wave starts on its own, and pausing then spamming your spells if things start to go bad. If you see a shadow or get a particularly obnoxious beacon in a bad place, just restart. It takes too long to deal with that and you don't lose shadow cores for restarting a level. Testing that on field I4 just now it took under two minutes to beat and it was worth 56,000xp. Testing H2, it took just under three minutes and was worth 106,000xp. There are 24 fields on those tiles. If they average 75k, for ~2000 shadow cores you can get almost two million xp in about an hour. Granted, it's not actually
adding two million xp to your total because you've already beat those fields. But maybe it's worth a million xp. It's a lot faster and easier to get that million xp this way than to suffer through tougher fields for it.
Then with that xp, go back and start over at F again and do them on harder settings and anger every wave you can. All of those fields in the E,F,I,H tiles are worth hundreds of thousands of xp and they're
much easier to do than later fields. For example, on F1 I have 234,000. On F2 I have 470,000. But for examle, on field M7, I only have 5732. Difficulty scales with the field. I was farming talismans on F1 with a 26x multiplier at wizard levels in the 60s. Whereas J5, for example, was a nasty horrible evil thing that I actually still haven't beat because I keep insisting on trying it with high multipliers and it keeps giving me near-million-health giants and spires and things.
Granted, I think my F2 score is inflated because of the shadow xp trick
described here. When that happens, great. Take advantage of it. Sometimes the shadow will utterly fail to find your orb and you can use that to add two to three hundred thousand xp to your score just for 10 minutes of sitting there watching the screen. Or you can use that time to farm acheivements. Sometimes you can get 10 at a time on a single field. Other times it attacks it right away, or you don't even get a shadow at all. But even without a shadow, with Haste, Beacon Storm, Mana Lock, Corrupted Banishment and Giant Domination all maxed on glaring, that's a 26x xp multiplier for the low price of 280 shadow cores. Which only takes about 15 minutes of sleeping while your computer macros for you to get.
But yeah, ~10,000 shadow cores, pretty easily.
Alternately, if you don't wantg to macro, you could probably get a similar result by simply saving up a couple hundred from regular play, then get into the habit of using something like haste 7, mana lock 2, beacon storm 2 on every field you play as you advance through the game. There are enough fields that drop 30-60 shadow cores for beating them that you'd probably come reasonably close to breaking even, and you'd get a ~4x score multiplier on every map you played for neglible extra difficulty. If you hve 2 million xp now, you could have 8 million instead simply by spending shadow cores as you get them on easy traits. You'll eventually end up selling all those fragments you've been upgrading anyway, and the benefit of being half again higher level is probably comparable or better to all the random orblet/curse/"xp for wizard level"etc bonuses on most fragments.