Lvl	Effect	MP	Duration
1	Atk Power +1	30	2:00
2	Atk Power +2	31	2:20
3	Atk Power +3	31	2:40
4	Atk Power +4	35	3:00
5	Atk Power +5	35	3:20
6	Atk Power +6	38	3:40
7	Atk Power +7	38	4:00
8	Atk Power +8	42	4:20
9	Atk Power +9	42	4:40
10	Atk Power +10	46	5:00
11	Atk Power +11	46	5:20
12	Atk Power +12	50	5:40
13	Atk Power +13	50	6:00
14	Atk Power +14	54	6:20
15	Atk Power +15	54	6:40
16	Atk Power +16	59	7:00
17	Atk Power +17	59	7:20
18	Atk Power +18	65	7:40
19	Atk Power +19	65	8:00
20	Atk Power +20	70	8:30

Raising the power of the bow by concentrating it.