Gunfire Reborn

Tao is the first character that you can buy with soul essence. She costs 400 Souls.

Once you have her unlocked the Blade Heart (Flying Swords) is your LB (E on PC). For every 15 ammo consumed, you will gain 1 stack of Blade Heart (default max stack is 6). Each stack can summon up to 3 swords at a time. If you really want you can just sit at the start and spam LB constantly. You'll get 2 stacks (by default) ever 4 seconds, however the more stacks you have the more swords come out per stack. If you have a fast shooting weapon, ex: laser gloves, you'll get stacks super fast and can spam this at max stacks.

Some perks to look out for are "sword Shadow" Summons 1 additional sword per level, and Luminous Heart makes your stacks higher and at lvl 3 you only need to consume 10 ammo per stack. If you solely focus on getting these two perks up to max and get a laser glove you should be able to get this cheevo in roughly 2 games getting to act 3 boss.

After you've summoned a total of 10,000 swords the achievement is yours!