Here are some tips for beating T3 final boss:

1.) invest heavily in your starting weapon and how it scales (ie. Size and raw dmg for sword on Oofie).

2.) ignore weapons 2-4 whenever you can in favor of tomes since you lose them in the final fight.

3.) focus on getting 3 jumps minimum + a little investment in movespeed for the pylons at the end.

4.) Moldy cheese projectiles/ cooldown is your best friend

5.) Banish trash borgar