msem-instigator

Whenever equipped creature attacks, put a charge counter on Shimmersting, then create a token that's a copy of equipped creature and that's tapped and attacking for each charge counter on Shimmersting, except the tokens aren't legendary. Exile the tokens at the beginning of the end step.
Equip {5}

{2}, {T}, Sacrifice Tunnel Map: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Ghastly Castle enters the battlefield tapped unless another player controls a land that could produce {U} or {B}.
{T}: Add {U} or {B}.

Gleaming Veldt enters the battlefield tapped unless another player controls a land that could produce {G} or {W}.
{T}: Add {G} or {W}.

Grisly Marsh enters the battlefield tapped unless another player controls a land that could produce {B} or {G}.
{T}: Add {B} or {G}.

Sunken Cavern enters the battlefield tapped unless another player controls a land that could produce {U} or {R}.
{T}: Add {U} or {R}.

Sunny Dunes enters the battlefield tapped unless another player controls a land that could produce {R} or {W}.
{T}: Add {R} or {W}.

Put target tapped creature and all other creatures with the same name as that creature on the bottom of their owners' libraries.

Choose one or all—
• Dreamfire deals X damage to target creature.
• Dreamfire deals X damage to each player.
• Target creature gets +X/+0 until end of turn.

Until end of turn, gain control of target creature and it gains haste and shimmer. Untap it. (Whenever it attacks this turn, create a tapped and attacking token that's a copy of it. Exile that token at the beginning of the end step.)

Equipped creature has first strike.
{R}: Equipped creature gets +1/+0 until end of turn.
Equip {2}