Firelord items are obtained from MOS market only or buying them from players if they sell.
What benefits i get from that gear ?
None, Firelord equipment is good as any normal gear, that you can find through grinding, crafting, forging etc...
Just saves you some time.
How i can get higher level than 10 firelord items?
You need to enchant those items.
Firelord items can be enchanted up to +14-+15
Enchanting is done at anvil, same was as normal gears.
NB: Firelord items may break during enchanting.
https://forums.mo.ee/viewtopic.php?f=3&t=11 -> Enchanting guide.
Firelord Shield

- Required defense level
10 Defense -> Small Fire Shield
15 Defense -> Small Fire Shield +1
25 Defense -> Small Fire Shield +2
35 Defense -> Small Fire Shield +3
40 Defense -> Fire Shield +4
45 Defense -> Fire Shield +5
50 Defense -> Fire Shield +6
60 Defense -> Large Fire Shield +7
70 Defense -> Large Fire Shield +8
80 Defense -> Large Fire Shield +9
90 Defense -> Firelord Shield +10
95 Defense -> Firelord Shield +11
105 Defense -> Firelord Shield +12
110 Defense -> Firelord Shield +13
115 Defense -> Firelord Shield +14
120 Defense -> Firelord Shield +15

- Required Accuracy level
10 Accuracy -> Firelord Keblade
15 Accuracy -> Firelord Keblade +1
25 Accuracy -> Firelord Keblade +2
35 Accuracy -> Firelord Keblade +3
40 Accuracy -> Firelord Keblade +4
45 Accuracy -> Firelord Keblade +5
50 Accuracy -> Firelord Keblade +6
60 Accuracy -> Firelord Keblade +7
70 Accuracy -> Firelord Keblade +8
80 Accuracy -> Firelord Keblade +9
90 Accuracy -> Firelord Keblade +10
95 Accuracy -> Firelord Keblade +11
105 Accuracy -> Firelord Keblade +12
115 Accuracy -> Firelord Keblade +13
120 Accuracy -> Firelord Keblade +14

- Required Strength level
10 Strength -> Boar Spear
15 Strength -> Spontoon +1
25 Strength -> warspear +2
35 Strength -> shadowspear +3
40 Strength -> Dragon Lance +4
45 Strength -> Qiang +5
50 Strength -> Demonspear +6
60 Strength -> Ancient Spear +7
70 Strength -> Guardian's Piercer +8
80 Strength -> Ebonsteel Impaler +9
90 Strength -> Spike of Eternity +10
95 Strength -> Stormfury Piercer +11
105 Strength -> Vindication Spear +12
115 Strength -> King's Legacy Spear +13
120 Strength -> Peacemaker +14

- Required defense level
10 Defense -> Soul Collector Helmet
15 Defense -> Soul Collector Helmet +1
25 Defense -> Soul Collector Helmet +2
35 Defense -> Soul Collector Helmet +3
40 Defense -> Soul Collector Helmet +4
45 Defense -> Soul Collector Helmet +5
50 Defense -> Soul Collector Helmet +6
60 Defense -> Ancient Soul Collector Helmet +7
70 Defense -> Ancient Soul Collector Helmet +8
80 Defense -> Ancient Soul Collector Helmet +9
90 Defense -> Firelord helmet +10
95 Defense -> Firelord helmet +11
105 Defense -> Firelord helmet +12
110 Defense -> Firelord helmet +13
115 Defense -> Firelord helmet +14
120 Defense -> Firelord helmet +15

- Required defense level
10 Defense -> Firelord Platemail
15 Defense -> Firelord Platemail +1
25 Defense -> Firelord Platemail +2
35 Defense -> Firelord Platemail +3
40 Defense -> Firelord Platemail +4
45 Defense -> Firelord Platemail +5
50 Defense -> Firelord Platemail +6
60 Defense -> Firelord Platemail +7
70 Defense -> Firelord Platemail +8
80 Defense -> Firelord Platemail +9
90 Defense -> Firelord Platemail +10
95 Defense -> Firelord Platemail +11
105 Defense -> Firelord Platemail +12
110 Defense -> Firelord Platemail +13
115 Defense -> Firelord Platemail +14
120 Defense -> Firelord Platemail +15

- Required defense level
10 Defense -> Firelord Pants
15 Defense -> Firelord Pants +1
25 Defense -> Firelord Pants +2
35 Defense -> Firelord Pants +3
40 Defense -> Firelord Pants +4
45 Defense -> Firelord Pants +5
50 Defense -> Firelord Pants +6
60 Defense -> Firelord Pants +7
70 Defense -> Firelord Pants +8
80 Defense -> Firelord Pants +9
90 Defense -> Firelord Pants +10
95 Defense -> Firelord Pants +11
105 Defense -> Firelord Pants +12
110 Defense -> Firelord Pants +13
115 Defense -> Firelord Pants +14
120 Defense -> Firelord Pants +15

- Required defense level
10 Defense -> Firelord Boots
15 Defense -> Firelord Boots +1
25 Defense -> Firelord Boots +2
35 Defense -> Firelord Boots +3
45 Defense -> Firelord Boots +4
55 Defense -> Firelord Boots +5
60 Defense -> Firelord Boots +6
70 Defense -> Firelord Boots +7
80 Defense -> Firelord Boots +8
90 Defense -> Firelord Boots +9
95 Defense -> Firelord Boots +10
105 Defense -> Firelord Boots +11
110 Defense -> Firelord Boots +12
115 Defense -> Firelord Boots +13
120 Defense -> Firelord Boots +14