If we talk about the difficulty of inscription, ordinary runes are like drawing a tree on a canvas; once you've sketched the trunk and branches, the image takes shape. However, creating Lu'en runes requires delineating every vein of each leaf on that same canvas. Moreover, the technique often demands intricate and continuous strokes; any pause or error means starting over from scratch.

The difficulty is self-evident.

Su'en had tried before. Even with his multitasking abilities, his success rate for completing a fourth-tier mental Lu'en rune didn't exceed twenty percent.

That was already the normal success rate for ordinary rune masters.