+40% is a Treasure Card available for 1000 gold at Librarians from Krok up. There is also +40% Item Card available on various items. +35% is available from the regular Mythblade and Spirit Blade. +45% is available from sharpened blade on both Mythblade and Spirit Blade, available as learned, pet, item and treasure cards.
Sometimes I see people who uses a myth spell that adds 40% or 45% damage to the enemy, I only have 35% which is my mythblade.
Can somebody please tell me where you can get those spells because I keep looking it up but I can't find how.
Mythblade adds +35% to next , not 25%
However, if you're referring to the common Myth Traps then those add +25% Trap to an enemy. Treasure versions exist which add more (+35%, etc) and also, these normal (trained school spells) can be enchanted with spells from the school further increasing damage.
Are you at least a level 12 myth student and have the troll minion spell? If so, Cyrus drake should have a quest for you called 'Mything in Action' which will give you a 35% myth blade. If you still don't see the quest that's very strange. Also where did you learn a 25% myth blade?
I'm guessing you're talking about some sort of trap. Myth Traps in Treasure Card or Item Card form usually boost damage by 30% rather than the normal 25%. 35% Myth Traps are also possible with the use of the Potent Trap enchantment, which can be learned at Level 86 after doing a side quest. The Punklops card also gives a 35% Myth Trap (though I think I've seen the trap give 40% at one point), as well as an equally powerful Ice Trap.
One of the better ways to get more and better blades (for any school, not just myth) is to use the sharpen blade enchantment from the sun school. You can't get sharpened blade as a learned spell until level 86 in Azteca, but you can get item card versions from pets. The pet versions are just as useful as the learned versions. In particular the enchanted armament pet grants up to three sharpened blade cards, one as a newly hatched baby, a second when it reaches ancient, and a third when it reaches mega. Three seems a bit excessive to me so I usually stop training at ancient and work with two.
The enchanted armament drops from gladiator Dimachaerus in Olympus, you can farm him when you reach level 30. At level 30 you'd need a lot of help to defeat him. Or you can hatch with someone who already has one. I recommend the w101 central website for arranging hatching meetups (central calls this pet mixing meetups), you can copy and paste the url here:
Pets can be swapped between characters on the same account via your shared bank, so once you develop one you like you can pass it on to other wizards later.
, not 25%
school further increasing 
