Dota 6.49 comes with 3 additional bosses which are accessed using the 'letter' items dropped by killing the 'Ice Frogs' found at set locations on the map. To access the first boss, 3 frogs must be found and killed using an aoe stun with heroes such as lina and ursaar. The frogs are invisible so a gem is needed. Once the letter items are found, they combine to form an ice-orb like object named ???. Now to access the first boss, you must go the top left hand corner of the map where there is a portal. This portal will take you directly to the right bottom hand corner of the map where a shrine and a area to fight the boss is located. You will need either tree destroying heros such as lina or furion, or about 15-20 tangos to clear the trees at the top left. The first boss is a frost dragon similar to blue dragons in melee. Imagine the strength of a fourth level roshan. They come in 3 stages. Once the first boss is defeated, 4 more frogs will appear around the map in different but set locations. Repeat the process and the orb will form. The second boss is a massive wisp like creature, think kotrs ulti but like much bigger. It has about 20000 hp and 340+ attack damage. Once the second boss is killed, six more frogs will appear and once again an orb will form, except that it will be a fire orb. The third boss is a phoenix and its powerful as, needs 5 people and decent items. Once the third boss is killed, Kael appears, an almost unbeatable hero that has hp in the hundred thousands and 900+ attack damage. once killed he drops a powerful item, which grants a few things such as quadrupling damage and 522 movement speed.
1st round of frogs : 4
location :
1. sentinel base (under tavern)
2. sentinel forest (not in sentinel secret shop area, the other one) - check near neutral creeps
3. upper lane in scourge area (behind trees, between 1st and 2nd scourge tower)
4. near spawning artifact (bottom right of the map)
2nd round of frogs : 3
location :
1. scourge forest (not in sentinel secret shop area, the other one) - check behind trees
2. upper lane in scourge area (trees upper on that lane)
3. same as above - do the exploring job
3rd round of frogs : 6
location :
1. sentinel forest - in the hole (between 1st and 2nd tower)
2. sentinel secret shop area - in the hole as well
3. scourge ancient creep (behind trees)
4. scourge base (trees area)
5. near scourge base (trees area)
6. scourge secret shop (do the exploring)