General DiscussionHow do I search for games without an item.

Either with teammate = magnus or with item Mjolnir/maelstrom will be your best bet. I dont think there is an excluding item filter.

He wants to know the efficiency of not going battlefury in the search engine..

AM without BF is mostly losing games for AM, in such games making a BF is like a guaranteed loss, so the players try to rush manta to get that power spike early. So it's probably gonna show you a higher loss rate on that.

Probable causes:
1) Bad AM pick against steamroll lineup.
2) Bad mid/offlaner, who can't make space for AM.
3) Shit AM that can't farm.

OR

Someone is trying out new stuff.

TL;Dr
The raw win rate data for AM without Bf won't be that helpful.