wtf i had to do in Teacher's archive

[Howl]

i killed the boss but idk what i have to do now? i cant walk in this ♥♥♥♥♥♥ water(acid)

[Desticler]

Find Isma's Tear in Royal Waterways to become immune to acid.

[Howl]

and where is this?

[Desticler]

Originally posted by Captain Lance:

and where is this?

In Isma's Grove.
There's a tunnel in Royal Waterways that connects City of Tears and Ancient Basin. In it, there's a horizontal hole filled with spikes. Approach it from the left (A completely different part of Royal Waterways, use map) and use Crystal Heart to go there, then it's just a mater of time until you find it.
Also, if you didn't beat Dung Defender yet, Isma's Grove will be filled with acid, so do that first if you didn't yet.

[⬧Towers⬧]

You can use cristal dash here so isma's tear is not needed but if you don't find how to go through this acid isma's tear is after beating the dung defender.

[Howl]

okokpomkokolsysyvxymlfdl i found it ty