"Tree Golem", don't you mean "Ent"?
A cool mechanic could be spawning a tree where the Ent/Tree Golem dies (if it is possible), instead of drop wood
"Young" Ent/Tree Golem/Treen't
400/600/800 hp
40/50/60 damage on contact
10/15/20 defense
Ent/Tree Golem/Treen't AI
Rare enemy category
50% Knockback resistance
(Spawn after WoF has been defeated)
30%/50% chance to drop any fruit of the "Forest's Tree" Pool drop, between 1-3 fruits
100% chance to drop between 1-6 Accorns
100% chance to drop between 20-60 wood
Ent/Tree Golem/Treen't
600/900/1200 hp
50/60/80 damage on contact
15/20/25 defense
Ent/Tree Golem/Treen't AI
Rare enemy category
80% Knockback resistance
(Spawn after a Mech Boss has been defeated)
50%/100% chance to drop any fruit of the "Forest's Tree" Pool Drop, between 2-4 fruits
100% chance to drop between 2-8 Accorns
100% chance to drop between 50-80 wood
"Old" Ent/Tree Golem/Treen't
900/1500/1800 hp
70/100/150 damage on contact
20/30/40 defense
Ent/Tree Golem/Treen't AI
Rare enemy category
100% Knockback resistance
(Spawn after Plantera has been defeated)
100% chance to drop any fruit of the "Forest's Tree" Pool Drops, between 3-6
100% chance to drop between 8-10 Accorns
100% chance to drop between 80-150 wood
All these trees are inmune to: Poisoned, Acid Venom, Confused and Wet
All these trees have their own banner and don't stop spawning after the next tier is unlock
On Windy Days, all these Trees doubles their chance to Spawn every tick
Ent/Tree Golem/Treen't AI: "Will walk to the "player" (that is doing the highest DPS to this enemy).
Will ignore the players with lesser DPS.
Jump over 5 blocks as maximum to reach the "player".
Falls through platforms to reach the "player".
Will try to line up horizontally to the player first.
If fails to target the enemy will become "invulnerable".
While "invulnerable" starts an animation turning into a tree-like appearance.
While "invulnerable" the enemy can't take any damage.
Fails to target if "player" is higher to 6 blocks, "player" is far than 8 blocks.
What about this?
@MrD108