Virus of Yyahan + Octopus
Been a while since I hit a virus + tome of yyahan run but that strategy got a massive buff with the calc/retort/philo scaling being global and virus cd lowered a few patches ago. Still makes for the most entertaining run in the game with meticulous planning to make it work
For those who don't know, transforming a reagent on board in a fight with virus counts towards buffs provided by items like tome of yyahan, calcinator, retort, and philosopher's stone. You can cheese certain monster fights with a full board of reagents and a philo stone for regen to get 8 transforms and then pivot late game into something with the buffs you got. In this case I used the permanent regen from yyahan with staff of the moose to buff the octopus