2 New players.

[godbox]

at lvl 20 you can heal your pet for 220 hp for 100 mana or you can summon a new one which will have between 400 and 600 hps for 200 mana.
not sure if mages get any heal upgrades for pet past that but pets are always 200 mana so you just chain summon (start casting and dismiss at last possible second) instead of healing