Does anyone know where exactly should I climb to reach this guy?
Also, I’ve read a rumor that there’s a jumping trap near the Red Mother, that launches you right onto the shattered bridge the Watcher is standing on. is that true?
Of course, the bat spell. This is hilarious, I maxed my sorcery and now I forgot about the bat spell. Not to mention the climbing gloves/boots. They are rotting in my armory back in my Tundra base.
Thanks for the help!
I remembered the existence of climbing gloves/boots after maxing my sorcery because my asthmatic stamina would be insufficient for any kind of climbing.
The Ice Bridge spell also works: Approach from the platform southwest of the Watcher, where some Relic Hunters stand above the Red Mother. Use Ice Bridge to reach the tower. Only a very short climb later, you’re there.
Much safer, and those Relic Hunters carry good loot. 
Ice bridge from the bridge platform with the relic hunters on it just south of red mother.
Beat me to it.