It looks like your challenge is in executing the code. Your OnSelect statement will not work as written.
Basically, you need to put the code you want to execute into another control and then activate that control.
Code:
<Page Activated="true" eq2usescomwndcontrols="true" ExpandWin="263,400" Location="458,12" MaxSize="16384,16384" MinimumSize="235,325" MinSize="235,325" Name="LoreandLegend_Info" PackLocation="center,center" ScrollExtent="574,752" Size="574,752" Target.press="true" UserMovable="true">
<Button Name="OneButtonToRuleThemAll" OnPress="parent.Tier2Option.press=true" Option.press="true" Option.pressed="true" />
<Dropdownbox BackgroundOpacity="1.000" DataSource="TheButtons" Location="10,28" MaximumSize="16384,32" MinimumSize="50,32" Name="CopyAndPasteMe" OnSelect="parent.OneButtonToRuleThemAll.press=true parent.OneButtonToRuleThemAll.OnPress=("parent." ## SelectedItem.Target ## ".press=true" )" RowTemplate="/CommonElements.Dropdown.data.dropdown_template" ScrollExtent="200,32" SelectedItemIndex="1" Size="200,32" Style="/CommonElements.Dropdown.data.style" />
<DataSource Name="TheButtons">
<Data Name="Button1" Target="Tier1Option" Text="Gnoll" />
<Data Name="Button2" Target="Tier2Option" Text="Orc" />
</DataSource>
<Button Location="5,28" Name="Tier1Option" NormalTextColor="#00FF00" OnPress="Parent.Tier_1.Visible=True
Parent.Tier_2.Visible=False 
Parent.Tier_3.Visible=False 
Parent.Tier_4.Visible=False 
Parent.Tier_5.Visible=False 
Parent.Tier_6.Visible=False 
Parent.Tier_7.Visible=False 
Parent.Tier_8.Visible=False
Parent.Tier_9.Visible=False 
Parent.Tier_10.Visible=False 
Parent.Tier_11.Visible=False 
Parent.Tier_12.Visible=False 
Parent.Tier_13.Visible=False 
Parent.Tier_14.Visible=False
Parent.Tier_15.Visible=False
Parent.Tier_16.Visible=False
Parent.Tier_17.Visible=False
Parent.Tier_18.Visible=False
Parent.Tier_19.Visible=False
Parent.Tier_20.Visible=False
Parent.Tier_21.Visible=False
Parent.Tier_22.Visible=False
Parent.Tier_23.Visible=False
Parent.Tier_24.Visible=False
Parent.Tier_25.Visible=False
Parent.Tier_26.Visible=False
Parent.Tier_27.Visible=False
Parent.Tier_28.Visible=False
Parent.Tier_29.Visible=False
Parent.Tier_30.Visible=False
Parent.Tier_31.Visible=False
Parent.Tier_32.Visible=False
Parent.Tier_33.Visible=False
Parent.Tier_34.Visible=False
Parent.Tier_35.Visible=False
Parent.Tier_36.Visible=False
Parent.Tier_37.Visible=False
Parent.Tier_38.Visible=False
Parent.Tier_39.Visible=False
Parent.Tier_40.Visible=False
Parent.Tier_41.Visible=False
Parent.Tier_42.Visible=False
Parent.Tier_43.Visible=False
Parent.Tier_44.Visible=False
Parent.Tier_45.Visible=False
Parent.Tier_46.Visible=False
Parent.Tier_47.Visible=False
Parent.Tier_48.Visible=False
Parent.Tier_49.Visible=False
Parent.Tier_50.Visible=False
Parent.Tier_51.Visible=False
Parent.Tier_52.Visible=False
Parent.Tier_53.Visible=False

">Gnoll</Button>
<Button Location="4,55" Name="Tier2Option" NormalTextColor="#00FFFF" OnPress="Parent.Tier_1.Visible=False
Parent.Tier_2.Visible=True 
Parent.Tier_3.Visible=False 
Parent.Tier_4.Visible=False 
Parent.Tier_5.Visible=False 
Parent.Tier_6.Visible=False 
Parent.Tier_7.Visible=False 
Parent.Tier_8.Visible=False
Parent.Tier_9.Visible=False 
Parent.Tier_10.Visible=False 
Parent.Tier_11.Visible=False 
Parent.Tier_12.Visible=False 
Parent.Tier_13.Visible=False 
Parent.Tier_14.Visible=False
Parent.Tier_15.Visible=False
Parent.Tier_16.Visible=False
Parent.Tier_17.Visible=False
Parent.Tier_18.Visible=False
Parent.Tier_19.Visible=False
Parent.Tier_20.Visible=False
Parent.Tier_21.Visible=False
Parent.Tier_22.Visible=False
Parent.Tier_23.Visible=False
Parent.Tier_24.Visible=False
Parent.Tier_25.Visible=False
Parent.Tier_26.Visible=False
Parent.Tier_27.Visible=False
Parent.Tier_28.Visible=False
Parent.Tier_29.Visible=False
Parent.Tier_30.Visible=False
Parent.Tier_31.Visible=False
Parent.Tier_32.Visible=False
Parent.Tier_33.Visible=False
Parent.Tier_34.Visible=False
Parent.Tier_35.Visible=False
Parent.Tier_36.Visible=False
Parent.Tier_37.Visible=False
Parent.Tier_38.Visible=False
Parent.Tier_39.Visible=False
Parent.Tier_40.Visible=False
Parent.Tier_41.Visible=False
Parent.Tier_42.Visible=False
Parent.Tier_43.Visible=False
Parent.Tier_44.Visible=False
Parent.Tier_45.Visible=False
Parent.Tier_46.Visible=False
Parent.Tier_47.Visible=False
Parent.Tier_48.Visible=False
Parent.Tier_49.Visible=False
Parent.Tier_50.Visible=False
Parent.Tier_51.Visible=False
Parent.Tier_52.Visible=False
Parent.Tier_53.Visible=False


">Orc</Button>
In that code snippet, I kept your original buttons (except for taking out the spaces in the names). When you select a lore from the dropdown, the dropdown puts code into OneButtonToRuleThemAll.OnPress and presses that button which then presses the button which would originally have done the work in your page (that button now being invisible).
Whole file attached, but I did only do the first two buttons, hopefully it's enough to get you started.
Mother