lkajsdhkjash and eemjayy I dont know what Guardian you mean, but if you mean the corrupt wizard (the 5th epic and final battle) this might help ;-)
This is how I managed to kill him few mins ago, there might be other/better ways but at least this one worked for me(lvl 72(?)Wizard - now 74; max skill at the first 4 skills (mana and armor), gem creating and combining, cheaper buildings, pure gem mastery and high grade starter gems, all other points I spend to medium grade starter gems)
1. get your mana pool up to 19k and make sure to have at least 5200 mana (or close to and a orange gem *g*)
2. get some pure grade 6 gems (3 purple, 3 cyan, 4 green and 2 blue)
3. get towers (2 north of enemy base, 7-8 in 2 lines north of road, a hole line south up to the crossroad and 3 more near crossroad (at road that leads south)
4. build water trench all the way from base to crossroad and three on northern part of the U-turn
5. setting of gems:
- pruple close to base (2 north, 1 at road) switch the 2 from the base to crossroad when boss is out of range
- cyan 2 close to base that will be switched to crossroad (western part so they also cover the U-turn) the third in middle of southern line of towers
- green in southern line of tower 2 left 2 right of the cyan; the left ones have to switch to crossraod when boss is out of range and back; get one green in the south-eastern tower when boss passes and to the tower west of your base when boss is about to enter it
- one blue at the end of southern line of towers near croasroad and the other in secound row north of road which will be switched to the tower in the U-turn
- cause I had only 4600 mana when boss arived I had a orange gem (grade 5) to travle with the boss to get my 5200 mana for first lap
After this lap armor was about 50/120 and HP 90k/146k, so I get the 2 right greens in the towers north of the base instead of purple and also to crossroad so there were 4 green at crossroad in 2nd lap. I also got one of the green in the U-turn tower instead of the blue one (that was 5th tower south of road) to do some more dmg.
When the wizard was at U-turn the secound time he final died.
Some more hints (for all battles):
- with maxed "gem creation and combining" building gems up from grade 1 is the cheapest way to get gems of the kind you want (and gives some gold amulets for points)
- at lvl 27-39 with maxed skill dual gems are best cause of there fireing speed; at lvl 40+ its same for pure
- imo three+ color gems are waste of gems cause of the lag of boni dual and pure gems get
- two grade 6 gems are better than 1 grade 7 (as long as you have space for towers so both can fire at the enemy
- the specials of dual gems depend on how much parts (grade 1 gems) of each isused to combine them i.e. grade 6 red + grade 1 orange =!= grade 5 red + grade 5 orange even if its both times grade 6 red-orange
- red and lime gems are best for multiple targets at single (epic) bosses they lose their power
- cyan and lime have a cap for their specials at grade 6 (14% to shock, 40% to chain hit for pure, 70% of this for dual gems)
- always send in the next wave as long as you can handle it to get more mana
- try spend all your mana before last enemy dies to get some (more/better) amulets for more points
- dont give up on a battle you loose, try it some times, cause bad luck at getting gems (starters and normal) can make huge differences