ToME: the Tales of Maj'Eyal

What determines the strength of an iceblock? For example, I just hit Urkis with Ice Shards for 263 damage. He got frozen with a 420-point iceblock. Where did that number come from?

Also, it was a 3-turn iceblock. What determines that, given that Ice Shards doesn't specify a duration?

It depends on the skill.
Freeze, for example, freezes for X turns, with an ice block strength of 1.5 * (70 + 0.7 * (damage dealt by the spell without your cold damage multiplier)).
Ice damage, such as from Ice Shards, freezes for 2 turns with a block strength of 1.5 * (70 + 1.5 * (damage dealt by the spell without your cold damage multiplier)).
Glacial Vapour, for some reason, uses yet another calculation, namely 1.5 * (70 + 1.2 * (damage dealt by the spell without your cold damage multiplier)) with the same 2 turn duration.

TLDR: it's pretty inconsistent and I can see no pattern behind it, except that freeze duration is usually 2 turns except for the Freeze spell.

Note that these values are what I gained from a quick code skimming and may not be 100% accurate (and / or I may be overlooking things.)

Thank you!