Worth the troublesome run through seath's crack den to obtain.

I swear this is the hardest item to get in the game, no matter how much I hit the middle tail, no matter what weapons or spells I use it just never comes off.

Tips for cutting the tail: have a high damage, vertical slash weapon(2h greatsword or something similar), run to the immortality crystal, buff up beside it, and when seath starts attacking, run to the tail as he will break it himself and get stunned, giving you a huge window of opportunity.

easy tip when cutting tail:
don't hit the base, hit the tip of the tail
****er's tail quickly separated itself after 4 hits with my 30/30 quality claymore build

does reaching full reinforcement with this weapon give the max magic reinforcement trophy/achievement?

In my successful attempt (in NG++) in cutting his tail, it took me 30 minutes, 10 estus flasks and 10 humanity after getting hit by his tail wipe attack several times. Inbetween there were ~13 minutes of me just trying to get to his tail.

At some point, he did his super breath attack often enough for me to get enough hits in.

(Was fighting with my occult mace +5 as a cleric)

I almost killed Seath before managing to cut his tail, luckily I got it even though I died right after, 10000% worth it

My favorite ds1 build is a dragon bro magic build with this sword. Free fire from the dragon head, high int for versatile magics and also scaled sword AR. The rest can be vit, end, and min requirements for the rest.

Quick notes; The sword and magic wave can both hit and do damage if you catch an enemy right at the tip of the sword. Also, the wave can be either horizontal or vertical depending on if you swing one-handed or two.

My favorite sword. I love this thing. I don't know why, I just do. I love how it's been in every game so far (besides Sekiro but that makes sense since it's a different setting)