Instead of turning Knoll into a summoner, you could always turn him into a Druid.
Also, you no longer need distractions, as you're in the CC, or Creature Campaign, and can max out all of your characters' stats (Considering, of course, that you've visited all the Secret Shops during your playthrough)
Also, for every certain level in the tower, you get a certain secret character, for example, if you finish the the 3rd floor of the Tower of Valni, you get Caellech, ( a boos.)
The ff. are the levels you have to finish to get the secret characters: (Warning, may contain potential SPOILERS)
3rd Floor of the Tower of Valni: Caellech (Hero, a boss in one of the chapters[Where you are in a desert])
Finish the Lagdou Ruins: Fado (General, Eirika and Ephraim's dad, and former king of Renais.)
7th Floor of the Tower of Valni: Riev (Bishop, one of Vigarde's Generals, a boss in one of the chapters[Where you face Morva.])
Finish the all the floors in the Tower of Valni : Ismaire (Swordmaster, Joshua's mother, and Queen of Jehenna. The only time you can see her in-game is Eirika's route.)
5th Part of the Lagdou Ruins: You may get either Hayden (Ranger, King of Frelia, Innes and Tana's dad) or Glen (Wyvern Lord, Cormag's brother one of the Imperial Three[Glen, Dussel, Selena])
6th Floor of the Tower of Valni : Orson (Paladin, the one who was with Ephraim)
7th Part of the Lagdou Ruins: Valter (Wyvern Knight, boss in one of the chapters[In the desert, with Caellech.])
Finsh the Tower of Valni three times: Selena(Mage Knight, Boss in one of the Chapters and one of the Imperial Three[Glen, Dussel, Selena])
Finish the Lagdou Ruins three times: Lyon (Necromancer, pre-final boss)
Since most of the classes you're familiar with, let me explain something about the Necromancer class.
Think Druid mixed with Summoner. Lyon can summon stronger Phantoms than either Knoll or Ewan, and comes with the free Naglfar Tome, which you can use over and over again without fear of it running out.
Ismaire also comes with a free Wind Sword, as rare sword that acts like a Light Brand, but stronger, and effective against Air units.
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