I belive the highest you can get is level 100 talismans.
You'll be able to get higher leveld ones as you increase the difficulty you play on, haunting/glaring adds 20~ levels to them, and every perk you add, like mana lock, haste etc up to 7, adds levels to them aswell.
Level = rarity, yes. Oh and my mistake, it was rarity 73.
The fragment gives the following: +123 Initial Mana +15% Damage to Swarmlings +8% XP gained +16% Damage to reavers +51% Mana for starting waves early +14% Chance that gem bomb blasts summon +1 gem wasp (useless imo) +17% Damage to giants +1 To component skill levels (This gives all your gem skills +1 by default without having to spend skill points)
My current top talisman has 8/8 upgrades, and it's dark blue. Colors are grey, cyan, blue, yellow, red green, light green and orange. Might be more, but this is what I've seen so far.
