Arbor Earthcall, a WardenElementalist boss, specializes in earth magic. He will appear alone, but upon approach six Warden of Seasons will appear around him, which can be lured separately.
A very easy way to kill him is to use Pain Inverter, if his AoE spells hit enough creatures, it will heavily damage or downright kill him.
A big circle of Wardens of Seasons will pop-up around him, and heal him, if you venture too close to his spawning location. This pop-up is easily avoided by luring him away.
His aggro bubble is considerably larger than normal, so you don't need a bow to lure him.