ToME: the Tales of Maj'Eyal

Gather the threads does not work as described in the skill description. Supposed skill effect at my character level is +9.36 spellpower in the first turn, then a cumulative +1.56 every turn for five turns.

The actual effect is:
Turn 1: +3
Turn 2: +1
Turn 3: +0
Turn 4: +0
Turn 5: +0
Turn 6: +0
Turn 7: -4

Either there's some factor missing from the skill description or the skill is completely broken.

Spellpower, like any sort of power and saves, has diminishing returns. After 20 points every point costs 2, after 40 points every point costs 3 etc.