PREREQUISITESIn order to get ten Banish, you need one of the following, all of which will involve a level of filling the collection.
1) CollectionYou can power up to ten banishes by filling 100 entries in the collection.
2) DivanoPower up to four banishes, then use Divano as he starts with an extra 6. Divano is unlocked through the Crimson Shroud, evolution of Laurel and both Metaglio pieces.
3) RandomazzoPower up to eight banishes, then select XX - Silent Old Sanctuary as your randomazzo option for an additional three. XX is unlocked through reaching minute 31 on the Dairy Plant.
4) Queen SigmaIf you're coming to this update after finishing the game with a full collection, Queen Sigma comes with 108 banishes.
ACTUAL RUNGo to Il Molise, unlocked by reaching 30 minutes on any stage, as the enemies here don't move. Use Banish on a weapon every level.
If you'd rather get it done during normal play, either banish whenever you see an option you don't like, or wait until you're a higher level and you have two weapons that evolve with each other (Pugnala's guns, the Whip and Vento Sacro, Peachone and Ebony Wings) then when they evolve and you're already powerful, start banishing weapons now that you have a free weapon slot.