MH4U Teostra Guide

I will not be discussing his attacks since you can identify Teostra's attacks from the name itself. The purpose of this guide is to give you an idea on what you should do if Teostra executes these attacks. I haven't used any ranged weapon in MH4U so some of the counter moves are not applicable to ranged user. The first thing you need to do is to stay on Teostra's left side (your right side) all the time. Staying on the right has a lot of down side. Second is to always aim for Teorstra's LEFT back leg. Third, use ice element weapon because Teostra's back legs are weak to ice. Finally, run around (counter clockwise) it for a few seconds, stay close and observe Teostra's attacks. I will be adding references later.
Attacks

Normal Mode

Flame Aura - Do as much damage as you can to remove Teostra's aura. 0:28 to 0:48
Fire Breath - run at Teostra's left side since its fire breathe will start from right and will end at its right side. GS users always runs to its left side to do a Charged attack. 5:13 to 5:18
Back Hop - Time for you to chase it and attack once or twice. 0:38 to 0:43
Claw Swipe - ALWAYS roll to its LEFT side. Do not attack and observe.
Charge Attack/Forward Jump - It will run straight to you so try to run on Teostra's left side but not too far from it. 7:39 to 7:44
Explosion (Near) - Your target here is Teostra's tail. You can do combo, charge attack or for ranged you can attack its head but stay on its left side. 5:04 to 5:09
Explosion (Far) - Stay close and its your chance to attack Teostra's left leg, head or tail. 0:28 to 0:38
Tail Swipes - Attack Teostra's left leg once or twice. 5:22 to 5:25

Rage Mode

At this point, do not attack too much because Teostra's moves can be very dangerous. Practice the timing of your attacks at this phase because you will not be using the attack-and-roll move here. Just attack once or twice and observe Teostra's next move while waiting for the animation of your last attack is done, then walk. Rolling after your attack can be dangerous because you will be vulnerable during the roll animation (you only have 0.2 sec invincibility during a roll). Beware of the powders since it can be deadly if you have blast blight and hit by any of Teostra's attacks. ALWAYS cancel out that blast blight.

Powder Breathe - Same technique as Fire Breathe. Run on Teostra's left and attack once or twice. 1:11 to 1:17
Back Hop - Roll or run to the left since it will leave a blast cloud. This is the main reason why I always run/roll to its left side. You will have at least 10% chance of getting hit by the blast cloud 6:57. While rolling/running to the right has 70% chance 4:17. Sometimes I just walk to the left then attack once.
Claw Swipe - ALWAYS roll to its LEFT side. Observe. If you see that it will detonate the cloud, position yourself to its left leg then attack. If not, just run/walk counter clockwise. 1:27 to 1:29 and 1:49 to 1:51
Charge Attack/Forward Jump - Same as in normal mode.
Powder Blast (front) - attack Teostra's back legs or its tail. 1:15 to 1:20
Powder Blast (back) - attack Teostra's back legs by positioning yourself beside Teostra's front legs. 3:08 to 3:13
Tail Swipes - Another reason why I stayed on its left side. When Teostra does this and you are attacking Teostra's right back legs, there is a chance that you will be hit by the powder if you are too close. But when you are on the left side, there is a very low chance you will get hit by the powder. 2:12 to 2:14
Nova Explosion - I don't know how to call it but since it's like the super nova explosion, I just called it nova explosion. When it does this, run close to it as much as possible for a counter attack. 9:05 to 9:10
Super Nova Explosion - Use a count down timer and set it to 90 seconds because Teostra will be in rage mode for 100 seconds and will do this attack to switch to normal mode with flame aura. Some IG users use the kinsect effect as their timer. 2:30 to 2:37

Attack patterns are based on Guild Quest Level 140 Teostra. It may take 15-30mins depending on your skill. Try to hunt it alone. This will make you a better hunter and will never rely on group hunting. Good luck and happy hunting!!! Video credits to CantaPerMe on youtube.