Jeechwo appears in all Corridor stages n with n=x*8+3. Rarely drops a Tendai Uyaku. After defeating it, there is a chance to obtain its skin which can be used when merging minions. This minion's skin has the skinventory-ID 2.
All bosses in the Eternal Corridor use infinite Mana, which allows them to use their attacks as often as they wish. Constantly uses its Claw - ---- + Critical attack.
Hints on defeating this boss
Use a sleep combo or an earth-type minion and hope it will not score too many critical hits.