Dark Spike only continued to train his magic in the cave to further assure he gains his power. As he trained, he only had a few things in his mind trouble him. But he did not dwell on it further and continued to train.
He first trained on shapeshifting like the Changelings. First, he closed his eyes and focused his magic. then in dark green flames, transformed into numerous creatures and ponies. Turning from Twilight, Rarity, Rainbow Dash, Applejack, Big Macintosh, King Sombra, Chrysalis, Shining Armor, Princess Luna, Princess Celestia, Starlight Glimmer, Sunburst and finally his past young self both in pony and dragon form. As soon as he returned to his normal form, his eye pupils only glowed more blood red and the outside turned dark black even more, to the point where he cried out what appeared to be black makeup.
He next trained in using clones, he managed to create clones of Tirek, Sombra and Chrysalis, but was still having trouble doing so with other ponies or friends he remembered. As soon as he focused, he created clones of him, Twilight, Applejack, Rarity, Starlight, his younger self, Celestia, Luna, Cadance, Shining Armor, King Sombra, Chrysalis and Tirek,
(A few hours later)
Dark Spike was huffing and puffing from his training, his sweat falling down his head as he breathed in and out.
"Hmmm, now that I have increased my power, I guess it is time I have a little fun with some blasts from the past." Dark Spike said as he got up.
He walked out of his cave and looked around, seeing there was nobody around to witness him. He transformed into his past self and continued on his way.
He walked around the forest and his eyes had glowed from normal green to blood red, his vision had turned red and only the inanimate objects had glowed yellow. He looked around and saw a trail of gems leading to an pathway.
"Gems?" Dark Spike said in confusion
He followed the trail and only saw more small gems leading somewhere. As soon as he stopped, he saw it lead to a small cave.
"Guess this is the place." Dark Spike said
The dark dragon in disguise had entered the cave and looked around using his specialized night vision. He looked and saw there were numerous gems within the cave. As he looked, he gave a look of surprise as the cave had looked noticeably more familiar.
"Wait a minute! I remember this cave! It was when that dragon tried to kill me when that stupid owl of that hypocrite of a Princess made me feel unwanted and run away from the stupid library! Oh I've been waiting a LONG time for this!"
As Dark Spike looked, he sensed something behind him and turned around. The figure revealed himself to be a large green dragon with orange eyes and black pupils with light green spikes on his body.
"What are you doing here eating my gems?" The dragon asked
"I didn't eat them you overgrown fool, you left a trail to MY HOUSE!" Dark Spike said in bitter rage
"Do you really wish to perish now weak child?" The dragon said with a look of fury at the dark dragon's insult.
"Do YOU wish for me to rip out your both your head and spine? After what you did to me all those years ago?" Dark Spike said in malicious hatred
Hearing enough, the dragon chased Dark Spike (still in his past form), who teleported and blasted a large dark wave of fire at him.
The enraged dragon attacked Dark Spike, who easily toyed with him.
"Stop moving!" The dragon said trying to attack.
"Well, since you asked SO nicely." Dark Spike said with sarcasm
He instantly stopped and the dragon breathed fire at him. Dark Spike was engulfed by the flames and seemingly was scorched away from the fire.
"Shame he was young, but he should have heeded me." The dragon said with mock pity
"Yes he should." An all too familiar voice said
The dragon turned and to his shock, Dark Spike was fine and flying WITHOUT wings but with magic, giving him a look of fury.
"Now it's my turn." Dark Spike said
He teleported and powered up a green aura in his fist and punched it into the green dragon's stomach. The dragon let out a screech of pain and fell defeated. As he fell, Dark Spike only advanced with a menacing look on his face.
The dragon only gave a look at the dark dragon teen and said
"Wait, what have I done to wrong you? I promise I can make it right! Please!"
Dark Spike refused to listen or answer and grabbed the dragon's chest. He glowed dark green and was absorbing the fire from the beaten dragon, who only screamed in pain.
"NO!, PLEASE! STOOOOOOOOPPPPPP!"
"FIVE YEARS TOO LATE!" Dark Spike responded
"NOOOOOOOOOOO!" The dragon said before he was weakened by the blast, with a blinding light engulfing them.
As soon as it dissipated, the dragon was reduced to ashes and Dark Spike's power only vastly increased not just his magic, but his hatred, rage and shattered heart, which was further exemplified when his eyes began to cry both normal tears of sorrow, but also the blackened tears from before stemming from the rage and grief from his past neglect.
"How's that for a weakling you pest!" Dark Spike said, returning to his true form.
As Dark Spike looked around the cave, he looked at all the gems and said with a blank look on his face
"Nothing in this cave but old memories, and bad ones no less."
As Dark Spike only looked at the cave, he slowly left the area behind and headed his way out, speechless.
(Outside)
When he left the cave, Dark Spike only looked around and flew in the air. He only looked at night sky and said
"Where is it?"
Dark Spike flew more and noticed a familiar tree in sight: Zecora's hut.
"Next stop tomorrow, this timeline's amulet. That way my younger self can finally know the truth of what this forsaken excuse of a place really is. But first, I need to deal with Zecora."
Dark Spike only flew into the night sky, back to his cave.
(At Twilight's Castle)
Inside the castle, the lights were off and the thrones that each of the girls had were now silent and unmoving. But they slowly glowed red, particularly the one Spike sat on.
The dragon symbol on his throne had began to glow red in the eye and after a few seconds, it had lit up blood red and glowed, causing the throne to shake. After it stopped, the dragon symbol stopped shaking the throne and the glow had ceased in the darkness.