Confirmed — the skill does nothing at all right now, at any level.

The passive HP version (Improved HP Recovery, the warrior one) is wired up and does give you extra HP on the 10-second tick. Its MP twin was never connected: the tick adds the HP bonus and then uses a flat base MP number with no skill bonus at all. So every point you put into Improved MP Recovery was wasted.

One thing I want to be straight about, because it affects the tooltip you photographed. The vague wording — "Constant additional recovery of MP" with no number, identical on the current and next level — is not our text. That is exactly what the original 2009 data says for this skill, and the original data also carries no number for it anywhere; the actual MP amount was baked into Nexon's client and isn't recoverable from anything we have. So I'm not going to invent a number out of thin air. Instead I'm using the curve from the two skills in the same game that share this skill's name and description word for word (the Crusader and White Knight "Improving MP Recovery"): +2 MP per level up to level 10, then +1 per level after. That puts you at +6 MP per tick right now at level 3, and +26 at master.

The tooltip text itself stays as-is, since it's the authentic string.

Confirmed — the skill did nothing at all, at any level. The warrior version (Improved HP Recovery) was wired into the 10-second tick; its MP twin never was, so the tick added the HP bonus and then used a flat base MP number with no skill bonus. Every point you put in was wasted. That's fixed now.

One correction to what I told you earlier in this thread. I'd said I would borrow the flat +2-per-level curve from the Crusader/White Knight "Improving MP Recovery" skills. That was the wrong call: your skill's own description says "the higher the level of the CHARACTER and the skill level", and a flat per-level curve has no character-level term in it at all, so it can't be right. The one place in any of our reference sources that actually implements this specific skill scales it by both, and that's what I've used: the tick becomes (skill level x character level x 0.1) + 3 MP, never less than the normal 3.

At your level 9 with 3 points in it that's 5 MP per tick instead of 3; it grows fast with your level — at level 100 with the skill maxed it's over 100 MP every 10 seconds. Note the game caps any single regen tick at 115, so very high levels will hit that ceiling.

The tooltip wording stays exactly as it is. "Constant additional recovery of MP" with no number, identical on the current and next level, is the authentic 2009 string — that's not our text and there is no number in the original data to put there.