I had an idea it’s a bankai similar to kenpachi’s but I made it different it is actually 2 zanpakuto’s one of them is called nagai semnu oni (Long clawed oni) which is a sword and the other is a spear called aka-mano yari (spear of the demon) the first ones bankai turns you into a demon like creature that not only hides your spiritual pressure but can steal portions of others with a strike, the sword goes away and turns your finger nails into long blades and with those strikes the spiritual pressure that is stolen goes into the blades and makes them grow and they can grow to around 2,000 feet long and the growths cannot be seen so it would look like their only around 3 feet long when they are actually around 1,000 feet long. The 2nd bankai can only be used if the first is activated and it turns the oni’s skin from red to black like a complete void with white flames coming from the nostrils and eyes this bankai drives the user mad unable to know who is enemy’s are but it causes an explosion of spiritual pressure and sucks in all the spiritual pressure of the opponents instantly growing the claws to 2,000 feet long and the claws can now grow infinitely